Fortress ponies are definably not meant to be in Nido's mod (they are far to tiny as they are the same size as dwarfs) but you may have them if you want.
I'll try to post them though am not sure how.
body_pony.txt
body_pony
[OBJECT:BODY]
[BODY:PONY_FORTRESS]
[BP:UB:upper body:upper bodies][UPPERBODY][CATEGORY:BODY_UPPER]
[DEFAULT_RELSIZE:1000]
[BP:LB:lower body:lower bodies][CON:UB][LOWERBODY][CATEGORY:BODY_LOWER]
[DEFAULT_RELSIZE:1000]
[BP:HD:head:STP][CON:UB][HEAD][CATEGORY:HEAD]
[DEFAULT_RELSIZE:300]
[BP:RA:right front leg:STP][CON:UB][LIMB]
[CATEGORY:LEG_FRONT]
[DEFAULT_RELSIZE:900]
[BP:LA:left front leg:STP][CON:UB][LIMB]
[CATEGORY:LEG_FRONT]
[DEFAULT_RELSIZE:900]
[BP:RH:right front hoof:right front hooves][CON:RA][GRASP]
[EMBEDDED][CATEGORY:HOOF_FRONT]
[DEFAULT_RELSIZE:120]
[BP:LH:left front hoof:left front hooves][CON:LA][GRASP]
[EMBEDDED][CATEGORY:HOOF_FRONT]
[DEFAULT_RELSIZE:120]
[BP:RL:right rear leg:STP][CON:LB][LIMB]
[CATEGORY:LEG_REAR]
[DEFAULT_RELSIZE:900]
[BP:LL:left rear leg:STP][CON:LB][LIMB]
[CATEGORY:LEG_REAR]
[DEFAULT_RELSIZE:900]
[BP:RF:right rear hoof:right rear hooves][CON:RL][STANCE]
[EMBEDDED][CATEGORY:HOOF_REAR]
[DEFAULT_RELSIZE:120]
[BP:LF:left rear hoof:left rear hooves][CON:LL][STANCE]
[EMBEDDED][CATEGORY:HOOF_REAR]
[DEFAULT_RELSIZE:120]
creature_pony_fortress.txt
creature_pony_fortress
[OBJECT:CREATURE]
[CREATURE:PONY_FORTRESS]
[DESCRIPTION:A short, sturdy equine fond of drink and industry.]
[NAME:fortress pony:fortress ponies:fortress pony]
[CASTE_NAME:fortress pony:fortress ponies:fortress pony]
[CREATURE_TILE:'p'][COLOR:3:0:0]
[CREATURE_SOLDIER_TILE:'P']
[INTELLIGENT]
[TRANCES]
[BENIGN]
[CANOPENDOORS]
[PREFSTRING:beards]
[BODY:PONY_FORTRESS:TAIL:2EYES:2EARS:NOSE:2LUNGS:HEART:GUTS:ORGANS:THROAT:NECK:SPINE:BRAIN:SKULL:MOUTH:FACIAL_FEATURES:TEETH:RIBCAGE]
[BODY_DETAIL_PLAN:STANDARD_MATERIALS]
[USE_MATERIAL_TEMPLATE:HOOF:HOOF_TEMPLATE]
[BODY_DETAIL_PLAN:STANDARD_TISSUES]
[USE_TISSUE_TEMPLATE:HOOF:HOOF_TEMPLATE]
[BODY_DETAIL_PLAN:VERTEBRATE_TISSUE_LAYERS:SKIN:FAT:MUSCLE:BONE:CARTILAGE]
[BODY_DETAIL_PLAN:BODY_HAIR_TISSUE_LAYERS:HAIR]
[USE_TISSUE_TEMPLATE:EYEBROW:EYEBROW_TEMPLATE]
[TISSUE_LAYER:BY_CATEGORY:HEAD:EYEBROW:ABOVE:BY_CATEGORY:EYE]
[USE_TISSUE_TEMPLATE:EYELASH:EYELASH_TEMPLATE]
[TISSUE_LAYER:BY_CATEGORY:EYELID:EYELASH:FRONT]
[SELECT_TISSUE_LAYER:HEART:BY_CATEGORY:HEART]
[PLUS_TISSUE_LAYER:SKIN:BY_CATEGORY:THROAT]
[TL_MAJOR_ARTERIES]
[BODY_DETAIL_PLAN:FACIAL_HAIR_TISSUES]
[BODY_DETAIL_PLAN:STANDARD_HEAD_POSITIONS]
[BODY_DETAIL_PLAN:HUMANOID_RIBCAGE_POSITIONS]
[RELSIZE:BY_CATEGORY:LIVER:300]
[USE_MATERIAL_TEMPLATE:SINEW:SINEW_TEMPLATE]
[TENDONS:LOCAL_CREATURE_MAT:SINEW:200]
[LIGAMENTS:LOCAL_CREATURE_MAT:SINEW:200]
[HAS_NERVES]
[USE_MATERIAL_TEMPLATE:BLOOD:BLOOD_TEMPLATE]
[BLOOD:LOCAL_CREATURE_MAT:BLOOD:LIQUID]
[CREATURE_CLASS:GENERAL_POISON]
[GETS_WOUND_INFECTIONS]
[GETS_INFECTIONS_FROM_ROT]
[USE_MATERIAL_TEMPLATE:PUS:PUS_TEMPLATE]
[PUS:LOCAL_CREATURE_MAT:PUS:LIQUID]
[PHYS_ATT_RANGE:STRENGTH:450:950:1150:1250:1350:1550:2250] +
[PHYS_ATT_RANGE:AGILITY:150:600:800:900:1000:1100:1500] -
[PHYS_ATT_RANGE:TOUGHNESS:450:950:1150:1250:1350:1550:2250] +
[MENT_ATT_RANGE:ANALYTICAL_ABILITY:450:950:1150:1250:1350:1550:2250] +
[MENT_ATT_RANGE:FOCUS:700:1200:1400:1500:1600:1800:2500] ++
[MENT_ATT_RANGE:CREATIVITY:450:950:1150:1250:1350:1550:2250] +
[MENT_ATT_RANGE:PATIENCE:450:950:1150:1250:1350:1550:2250] +
[MENT_ATT_RANGE:MEMORY:450:950:1150:1250:1350:1550:2250] +
[MENT_ATT_RANGE:SPATIAL_SENSE:700:1200:1400:1500:1600:1800:2500] ++
[BODY_SIZE:0:0:3000]
[BODY_SIZE:1:168:15000]
[BODY_SIZE:12:0:60000]
[BODY_APPEARANCE_MODIFIER:HEIGHT:75:95:98:100:102:105:125]
[APP_MOD_IMPORTANCE:500]
[BODY_APPEARANCE_MODIFIER:BROADNESS:75:95:98:100:102:105:125]
[APP_MOD_IMPORTANCE:500]
[SET_BP_GROUP:BY_CATEGORY:EYE]
[BP_APPEARANCE_MODIFIER:CLOSE_SET:0:70:90:100:110:130:200]
[APP_MOD_NOUN:eyes:PLURAL]
[BP_APPEARANCE_MODIFIER:DEEP_SET:0:70:90:100:110:130:200]
[APP_MOD_NOUN:eyes:PLURAL]
[BP_APPEARANCE_MODIFIER:ROUND_VS_NARROW:0:70:90:100:110:130:200]
[APP_MOD_NOUN:eyes:PLURAL]
[BP_APPEARANCE_MODIFIER:LARGE_IRIS:25:70:90:100:110:130:200]
[APP_MOD_NOUN:eyes:PLURAL]
[APP_MOD_DESC_RANGE:30:60:90:110:150:190]
[SET_BP_GROUP:BY_CATEGORY:LIP]
[BP_APPEARANCE_MODIFIER:THICKNESS:50:70:90:100:110:130:200]
[APP_MOD_NOUN:lips:PLURAL]
[APP_MOD_DESC_RANGE:55:70:90:110:150:190]
[SET_BP_GROUP:BY_CATEGORY:NOSE]
[BP_APPEARANCE_MODIFIER:BROADNESS:25:70:90:100:110:130:200]
[APP_MOD_DESC_RANGE:30:60:90:110:150:190]
[BP_APPEARANCE_MODIFIER:LENGTH:25:70:90:100:110:130:200]
[APP_MOD_DESC_RANGE:30:60:90:110:150:190]
[BP_APPEARANCE_MODIFIER:UPTURNED:0:70:90:100:110:130:200]
[BP_APPEARANCE_MODIFIER:CONVEX:0:70:90:100:110:130:200]
[APP_MOD_NOUN:nose bridge:SINGULAR]
[SET_BP_GROUP:BY_CATEGORY:EAR]
[BP_APPEARANCE_MODIFIER:SPLAYED_OUT:0:70:90:100:110:130:200]
[APP_MOD_NOUN:ears:PLURAL]
[BP_APPEARANCE_MODIFIER:BROADNESS:90:95:98:100:102:105:110]
[APP_MOD_IMPORTANCE:700]
[APP_MOD_NOUN:ears:PLURAL]
[APP_MOD_DESC_RANGE:91:94:98:102:106:109]
[BP_APPEARANCE_MODIFIER:HEIGHT:90:95:98:100:102:105:110]
[APP_MOD_IMPORTANCE:700]
[APP_MOD_NOUN:ears:PLURAL]
[APP_MOD_DESC_RANGE:91:94:98:102:106:109]
[SET_BP_GROUP:BY_CATEGORY:TOOTH]
[BP_APPEARANCE_MODIFIER:GAPS:0:70:90:100:110:130:200]
[APP_MOD_NOUN:teeth:PLURAL]
[SET_BP_GROUP:BY_CATEGORY:THROAT]
[BP_APPEARANCE_MODIFIER:DEEP_VOICE:0:70:90:100:110:130:200]
[BP_APPEARANCE_MODIFIER:RASPY_VOICE:0:70:90:100:110:130:200]
[SET_BP_GROUP:BY_CATEGORY:HEAD]
[BP_APPEARANCE_MODIFIER:BROADNESS:90:95:98:100:102:105:110]
[APP_MOD_IMPORTANCE:700]
[APP_MOD_DESC_RANGE:91:94:98:102:106:109]
[BP_APPEARANCE_MODIFIER:HEIGHT:90:95:98:100:102:105:110]
[APP_MOD_IMPORTANCE:700]
[APP_MOD_DESC_RANGE:91:94:98:102:106:109]
[MAXAGE:150:170]
[ATTACK:KICK:BODYPART:BY_CATEGORY:HOOF_FRONT]
[ATTACK_SKILL:GRASP_STRIKE]
[ATTACK_VERB:kick:kicks]
[ATTACK_CONTACT_PERC:100]
[ATTACK_PRIORITY:MAIN]
[ATTACK_FLAG_WITH]
[ATTACK:KICK:BODYPART:BY_CATEGORY:HOOF_REAR]
[ATTACK_SKILL:STANCE_STRIKE]
[ATTACK_VERB:buck:bucks]
[ATTACK_CONTACT_PERC:100]
[ATTACK_PRIORITY:SECOND]
[ATTACK_FLAG_WITH]
[ATTACK:BITE:CHILD_BODYPART_GROUP:BY_CATEGORY:HEAD:BY_CATEGORY:TOOTH]
[ATTACK_SKILL:BITE]
[ATTACK_VERB:bite:bites]
[ATTACK_CONTACT_PERC:100]
[ATTACK_PENETRATION_PERC:100]
[ATTACK_FLAG_EDGE]
[ATTACK_PRIORITY:SECOND]
[ATTACK_FLAG_CANLATCH]
[BABY:1]
[GENERAL_BABY_NAME:newborn foal:newborn foals]
[CHILD:12]
[GENERAL_CHILD_NAME:foal:foals]
[EQUIPS]
[CAVE_ADAPT]
[DIURNAL]
[PROFESSION_NAME:CRAFTSMAN:craftspony:craftsponies]
[PROFESSION_NAME:FISHERMAN:fisherpony:fisherponies]
[PROFESSION_NAME:HAMMERMAN:hammerpony:hammerponies]
[PROFESSION_NAME:SPEARMAN:spearpony:spearponies]
[PROFESSION_NAME:CROSSBOWMAN:markspony:marksponies]
[PROFESSION_NAME:AXEMAN:axepony:axeponies]
[PROFESSION_NAME:SWORDSMAN:swordspony:swordsponies]
[PROFESSION_NAME:MACEMAN:macepony:maceponies]
[PROFESSION_NAME:PIKEMAN:pikepony:pikeponies]
[PROFESSION_NAME:BOWMAN:bowpony:bowponies]
[PROFESSION_NAME:MASTER_CROSSBOWMAN:Elite Markspony:Elite Marksponies]
[PROFESSION_NAME:MASTER_BOWMAN:Elite Bowpony:Elite Bowponies]
[SPEECH:pony_fortress.txt]
[HOMEOTHERM:10067]
[SWIMS_LEARNED][SWIM_SPEED:2500]
[PERSONALITY:IMMODERATION:0:55:100]
[PERSONALITY:VULNERABILITY:0:45:100]
[PERSONALITY:STRAIGHTFORWARDNESS:0:55:100]
[MANNERISM_NOSE:nose]
[MANNERISM_EAR:ear]
[MANNERISM_HEAD:head]
[MANNERISM_EYES:eyes]
[MANNERISM_MOUTH:mouth]
[MANNERISM_HAIR:mane]
[MANNERISM_CHEEK:cheek]
[MANNERISM_TONGUE:tongue]
[MANNERISM_LEG:leg]
[MANNERISM_LAUGH]
[MANNERISM_SMILE]
[MANNERISM_WALK]
[MANNERISM_SIT]
[MANNERISM_BREATH]
[MANNERISM_POSTURE]
[MANNERISM_STRETCH]
[MANNERISM_EYELIDS]
[SPOUSE_CONVERSION_TARGET]
[CASTE:FEMALE]
[FEMALE]
[MULTIPLE_LITTER_RARE]
[CASTE:MALE]
[MALE]
[BODY_DETAIL_PLAN:FACIAL_HAIR_TISSUE_LAYERS]
[SELECT_CASTE:ALL]
[SET_TL_GROUP:BY_CATEGORY:HEAD:HAIR]
[PLUS_TL_GROUP:BY_CATEGORY:HEAD:CHEEK_WHISKERS]
[PLUS_TL_GROUP:BY_CATEGORY:HEAD:CHIN_WHISKERS]
[PLUS_TL_GROUP:BY_CATEGORY:HEAD:MOUSTACHE]
[PLUS_TL_GROUP:BY_CATEGORY:HEAD:SIDEBURNS]
[PLUS_TL_GROUP:BY_CATEGORY:HEAD:EYEBROW]
[PLUS_TL_GROUP:BY_CATEGORY:HEAD:EYELASH]
[TL_COLOR_MODIFIER:AMBER:1:AUBURN:1:BLACK:1:BROWN:1:BUFF:1:BURNT_SIENNA:1:BURNT_UMBER:1:CHARCOAL:1:CHESTNUT:1:CHOCOLATE:1:CINNAMON:1:COPPER:1:DARK_BROWN:1:DARK_CHESTNUT:1:DARK_TAN:1:ECRU:1:FLAX:1:GOLD:1:GOLDEN_YELLOW:1:GOLDENROD:1:LIGHT_BROWN:1:MAHOGANY:1:OCHRE:1:PALE_BROWN:1:PALE_CHESTNUT:1:PUMPKIN:1:RAW_UMBER:1:RUSSET:1:SAFFRON:1:SEPIA:1:TAN:1:TAUPE_DARK:1:TAUPE_GRAY:1:TAUPE_MEDIUM:1:TAUPE_PALE:1:TAUPE_SANDY:1]
[TLCM_NOUN:hair:SINGULAR]
[TL_COLOR_MODIFIER:GRAY:1]
[TLCM_NOUN:hair:SINGULAR]
[TLCM_TIMING:ROOT:80:0:130:0]
[TL_COLOR_MODIFIER:WHITE:1]
[TLCM_NOUN:hair:SINGULAR]
[TLCM_TIMING:ROOT:130:0:150:0]
[SET_TL_GROUP:BY_CATEGORY:HEAD:EYEBROW]
[TISSUE_LAYER_APPEARANCE_MODIFIER:LENGTH:50:80:90:100:110:120:150]
[APP_MOD_NOUN:eyebrows:PLURAL]
[APP_MOD_DESC_RANGE:55:70:90:110:130:145]
[TISSUE_LAYER_APPEARANCE_MODIFIER:DENSE:50:80:90:100:110:120:150]
[APP_MOD_NOUN:eyebrows:PLURAL]
[APP_MOD_DESC_RANGE:55:70:90:110:130:145]
[TISSUE_LAYER_APPEARANCE_MODIFIER:HIGH_POSITION:0:70:90:100:110:130:200]
[APP_MOD_NOUN:eyebrows:PLURAL]
[SET_TL_GROUP:BY_CATEGORY:HEAD:EYELASH]
[TISSUE_LAYER_APPEARANCE_MODIFIER:LENGTH:50:80:90:100:110:120:150]
[APP_MOD_NOUN:eyelashes:PLURAL]
[APP_MOD_DESC_RANGE:55:70:90:110:130:145]
[SET_TL_GROUP:BY_CATEGORY:HEAD:HAIR]
[PLUS_TL_GROUP:BY_CATEGORY:HEAD:CHEEK_WHISKERS]
[PLUS_TL_GROUP:BY_CATEGORY:HEAD:CHIN_WHISKERS]
[PLUS_TL_GROUP:BY_CATEGORY:HEAD:MOUSTACHE]
[PLUS_TL_GROUP:BY_CATEGORY:HEAD:SIDEBURNS]
[TISSUE_LAYER_APPEARANCE_MODIFIER:LENGTH:0:0:0:0:0:0:0]
[APP_MOD_NOUN:hair:SINGULAR]
[APP_MOD_RATE:1:DAILY:0:1000:0:0:NO_END]
[APP_MOD_DESC_RANGE:10:25:75:125:200:300]
[TISSUE_LAYER_APPEARANCE_MODIFIER:CURLY:0:70:90:100:110:130:200]
[APP_MOD_NOUN:hair:SINGULAR]
[TISSUE_LAYER_APPEARANCE_MODIFIER:GREASY:0:70:90:100:110:130:200]
[APP_MOD_NOUN:hair:SINGULAR]
[TISSUE_LAYER_APPEARANCE_MODIFIER:DENSE:50:80:90:100:110:120:150]
[APP_MOD_NOUN:hair:SINGULAR]
[APP_MOD_DESC_RANGE:55:70:90:110:130:145]
[SET_TL_GROUP:BY_CATEGORY:HEAD:HAIR]
[TISSUE_STYLE_UNIT:HAIR:STANDARD_HAIR_SHAPINGS]
[TSU_NOUN:hair:SINGULAR]
[SET_TL_GROUP:BY_CATEGORY:HEAD:CHEEK_WHISKERS]
[PLUS_TL_GROUP:BY_CATEGORY:HEAD:CHIN_WHISKERS]
[TISSUE_STYLE_UNIT:BEARD:STANDARD_BEARD_SHAPINGS]
[TSU_NOUN:beard:SINGULAR]
[SET_TL_GROUP:BY_CATEGORY:HEAD:MOUSTACHE]
[TISSUE_STYLE_UNIT:MOUSTACHE:STANDARD_MOUSTACHE_SHAPINGS]
[TSU_NOUN:moustache:SINGULAR]
[SET_TL_GROUP:BY_CATEGORY:HEAD:SIDEBURNS]
[TISSUE_STYLE_UNIT:SIDEBURNS:STANDARD_SIDEBURNS_SHAPINGS]
[TSU_NOUN:sideburns:PLURAL]
[SET_TL_GROUP:BY_CATEGORY:ALL:SKIN]
[TL_COLOR_MODIFIER:BROWN:1:BURNT_UMBER:1:CINNAMON:1:COPPER:1:DARK_BROWN:1:DARK_PEACH:1:DARK_TAN:1:ECRU:1:PALE_BROWN:1:PALE_CHESTNUT:1:PALE_PINK:1:PEACH:1:PINK:1:RAW_UMBER:1:SEPIA:1:TAN:1:TAUPE_PALE:1:TAUPE_SANDY:1]
[TLCM_NOUN:skin:SINGULAR]
[TISSUE_LAYER_APPEARANCE_MODIFIER:WRINKLY:0:0:0:0:0:0:0]
[APP_MOD_RATE:1:YEARLY:0:100:60:0:NO_END]
[APP_MOD_NOUN:skin:SINGULAR]
[APP_MOD_DESC_RANGE:0:0:0:1:25:50]
[SET_TL_GROUP:BY_CATEGORY:EYE:EYE]
[TL_COLOR_MODIFIER:IRIS_EYE_AMETHYST:1:IRIS_EYE_AQUAMARINE:1:IRIS_EYE_BRASS:1:IRIS_EYE_BRONZE:1:IRIS_EYE_COBALT:1:IRIS_EYE_COPPER:1:IRIS_EYE_EMERALD:1:IRIS_EYE_GOLD:1:IRIS_EYE_HELIOTROPE:1:IRIS_EYE_JADE:1:IRIS_EYE_OCHRE:1:IRIS_EYE_RAW_UMBER:1:IRIS_EYE_RUST:1:IRIS_EYE_SILVER:1:IRIS_EYE_SLATE_GRAY:1:IRIS_EYE_TURQUOISE:1]
[TLCM_NOUN:eyes:PLURAL]
entity_pony_fortress.txt
Ok this one is just to damn long to fix all the weird spaces. So what you do is this:
*You take the "entity_default.txt" file and copy it into the same directory.
*Change the name of the new file to "entity_pony_fortress.txt"
*Edit the file and replace "entity_defauly" on the top with "entity_pony_fortress".
*Also replace "[ENTITY:MOUNTAIN]" just below the last edit with "[ENTITY:PONY_FORTRESS]".
*Find the tag which reads "[ENTITY:FOREST]" and delete both it and EVERYTHING below it in the rest of the file.
*As an extra touch you can find the single noble tag that says dwarf and replace it with pony.
pony_fortress.txt (belongs in "data/speech/")
Who was to small to live
who ran from me like a frightened foal
who sucked plump helmets like a purring maggot
whose flank mark shattered on the anvil of my power
who forged [PRO_POS] own doom by challenging me
who was returned to the rock and muck from which it was spawned
whose tall tales of bravery were all the more embarrassing because of [PRO_POS] size
PS: I'm just a dolt with apparently to much time, all credit goes to the makers of the game and nido. It's a freaking miracle this thing doesn't kill itself.
EDIT: I have no idea what is going on with the first file, don't know if I can fix it.
PPS: THIS IS NOT COMPATABLE WITH NIDO's MOD!!! Do not replace any files!!!!!
EDIT: AARG!! I have no idea what is wrong with that first spoiler, it just doesn't WANT to work. Let me know it you have problems copy/paste it.