I tried this as well, but abandoned because Gobs don't have a military screen.
I atempted this at the same time as I tried to add Slade to the game as a useable ore: I got Slade Bars, but I can't forge it into stuff.
I recomend leaving Trolls and Ogres as sort of "sub-citizens" to marry and such, and using cave creatures for mounts. In my opinion, Giant Rats are a very goblin-esque mount.
trolls marry due to "[CAN_LEARN]" i think, which implies sentience. i have not changed this. interesting to note: trolls with professions cannot be trained into war trolls. giant rats have indeed been changed from exotic to common.
If you would post the mods you made to the Goblins, that would be helpful. I'd just do it myself, but I've got my Slade issue.
I'd like to make Slade a default material for Goblins, because of their demon lords.
Also, how would I go about making Nightwings a trainable/tameable/embarkable animal for Goblins?
to make nightwings tamable, find where they are stored in the raw files, and either change [PET_EXOTIC] to [PET], or just add [PET] if it does not have the exotic tag. i am unsure if this opens them up for embark, but if your civ leader has tamed them, you will have access at embark regardless of pet tags. (before changing pet tags, i had blizzard men embarkable with goblins)
Make some kind of obsidian-summoning altar so we can enjoy Dark Fortresses.
i wouldent know what it would do, or how to make it. i'm actually trying to modify the goblins at little as possible, while still rendering them playable.
raws thus far incoming. changes made so far:
*goblins are playable as both adventurers and in fortress mode
*nail tissue heals as fast as bone
*nerve tissue heals twice as slow as bone
*brain tissue heals ten times as slow as bone
*kobolds are no_eat and no_drink to survive worldgen
*most creatures in creatures_subterranean are now [PET] instead of [PET_EXOTIC]. non-pet creatures have not been changed.
*goblins can make coke out of coal and lignite
*goblins can cut gems
*goblins are active only in winter
*goblins have a broker
*goblins have an "auditor" (bookkeeper)
*goblins have a chief medical goblin
*goblins have a "warlord", a noble position that combines the duties of a militia commander, and a mayor.
*militia captains are "warband captains"
*trolls are [WAGON_PULLER] [MOUNT] [PACK ANIMAL] and [WAR_TRAINABLE]. they no longer [EQUIP]
*not a change but helpful to note, you can shear trolls, and spin their yarn into thread, and weave that into cloth.
*not changed - goblins are [NO_EAT] and [NO_DRINK] by default, to survive worldgen. i have not yet tested removing this tag.
please note, some of these changes can apply to dwarves as well, so you might want to use a separate world for your goblin towers.
i did not include the subterranean creatures raws, they exceed the post character limit. i am waiting on doing a proper upload till i am satisfied with the changes.