As much as I love being able to pick whether I want a dragon bone amulet or a dragon bone crown, it does cause a bit of reaction clutter that, to me at least, isn't essential. Even if we do want our choice of craft, one bit of redundancy can be eliminated without issue.
[REACTION:CARVE_BONE_CRAFTS_ADV]
[NAME:carve bone/tooth/horn crafts]
[ADVENTURE_MODE_ENABLED]
[REAGENT:carver:1:WEAPON:ITEM_WEAPON_DAGGER_LARGE:NONE:NONE][PRESERVE_REAGENT]
[REAGENT:bone:1:NONE:NONE:NONE:NONE][USE_BODY_COMPONENT][REACTION_CLASS:CARVE_SMALL]
[PRODUCT:100:1:CRAFTS:NONE:GET_MATERIAL_FROM_REAGENT:bone:NONE]
[SKILL:BONECARVE]
This demonstrates both efforts to reduce reaction clutter. The more useful one is once again the [REACTION_CLASS:CARVE_SMALL] part. By adding this to bone, tooth, horn, or other materials one deems suitable for small carved items, a whole lot of reactions can be distilled down to just one. Even if we retain separate reactions for amulets, rings, crowns, etc a lot of space is saved that way.
Similar results can be obtained for streamlining tanning. As far as I can tell, you made creature variations and applied them on a creature-by-creature basis. Makes sense for customizing the relative strengths of a creature's body materials, but that can still be done with slightly less complexity by making different "tiers" of material templates. As for tanning hides, there are easier options.
[REACTION:TAN_A_HIDE]
[NAME:tan a hide]
[BUILDING:TANNER:CUSTOM_T]
[REAGENT:A:1:NONE:NONE:NONE:NONE][USE_BODY_COMPONENT][REACTION_CLASS:SUPPLE_SKIN][UNROTTEN]
[HAS_MATERIAL_REACTION_PRODUCT:TAN_MAT]
In the product, if you want to use the reagent's material itself, use NONE instead of a reaction product class (TAN_MAT in this example).
[PRODUCT:100:1:SKIN_TANNED:NONE:GET_MATERIAL_FROM_REAGENT:A:TAN_MAT]
[SKILL:TANNER]
[AUTOMATIC]
[REACTION:TAN_A_HIDE_ADV]
[NAME:tan a hide]
[ADVENTURE_MODE_ENABLED]
[REAGENT:skin:1:NONE:NONE:NONE:NONE][USE_BODY_COMPONENT][UNROTTEN]
[HAS_MATERIAL_REACTION_PRODUCT:TAN_MAT]
[PRODUCT:100:1:SKIN_TANNED:NONE:GET_MATERIAL_FROM_REAGENT:skin:TAN_MAT]
[SKILL:TANNER]
This is nothing more than a replacement version of civ/fort tanning, and a simplified tanning reaction for adventurers. Scraper can be re-implemented according to taste, of course. The civ version looks for a "supple skin" REACTION_CLASS that I added to skin but not (untanned, as I'll clarify below) scale or chitin. This prevents oddities like chitin flasks.
The key of course is to add copies of the scale and chitin templates, designated as tanned equivalents of their respective materials. This also lets us rename the untanned materials "raw scale" and "raw chitin" to avoid player confusion. The name will show up for the butchered material, but won't affect descriptions of living creatures because it appears to look for TISSUE name instead.
Next we add to the original scale template:
[MATERIAL_REACTION_PRODUCT:TAN_MAT:LOCAL_CREATURE_MAT:TANNEDSCALE]
And add to the original chitin template:
[MATERIAL_REACTION_PRODUCT:TAN_MAT:LOCAL_CREATURE_MAT:TANNEDCHITIN]
Since these still use the TAN_MAT part, they can all be used by the same reaction, but with different result. Naturally, the final piece tying them all together goes in the BODY_DETAIL_PLAN files:
[BODY_DETAIL_PLAN:STANDARD_MATERIALS]
This command is just a shortcut for the similar lines (USE_MATERIAL_TEMPLATE|<token>|<template>) in a creature definition.
[ADD_MATERIAL:SKIN:SKIN_TEMPLATE]
[ADD_MATERIAL:FAT:FAT_TEMPLATE]
[ADD_MATERIAL:MUSCLE:MUSCLE_TEMPLATE]
[ADD_MATERIAL:BONE:BONE_TEMPLATE]
[ADD_MATERIAL:CARTILAGE:CARTILAGE_TEMPLATE]
[ADD_MATERIAL:HAIR:HAIR_TEMPLATE]
[ADD_MATERIAL:TOOTH:TOOTH_TEMPLATE]
[ADD_MATERIAL:EYE:EYE_TEMPLATE]
[ADD_MATERIAL:NERVE:NERVE_TEMPLATE]
[ADD_MATERIAL:BRAIN:BRAIN_TEMPLATE]
[ADD_MATERIAL:LUNG:LUNG_TEMPLATE]
[ADD_MATERIAL:HEART:HEART_TEMPLATE]
[ADD_MATERIAL:LIVER:LIVER_TEMPLATE]
[ADD_MATERIAL:GUT:GUT_TEMPLATE]
[ADD_MATERIAL:STOMACH:STOMACH_TEMPLATE]
[ADD_MATERIAL:GIZZARD:GIZZARD_TEMPLATE]
[ADD_MATERIAL:PANCREAS:PANCREAS_TEMPLATE]
[ADD_MATERIAL:SPLEEN:SPLEEN_TEMPLATE]
[ADD_MATERIAL:KIDNEY:KIDNEY_TEMPLATE]
[ADD_MATERIAL:LEATHER:LEATHER_TEMPLATE]
[ADD_MATERIAL:TALLOW:TALLOW_TEMPLATE]
[ADD_MATERIAL:SOAP:SOAP_TEMPLATE]
[ADD_MATERIAL:TANNEDSCALE:TANNED_SCALE_TEMPLATE]
[ADD_MATERIAL:TANNEDCHITIN:TANNED_CHITIN_TEMPLATE]
[BODY_DETAIL_PLAN:CHITIN_MATERIALS]
[ADD_MATERIAL:CHITIN:CHITIN_TEMPLATE]
[ADD_MATERIAL:FAT:FAT_TEMPLATE]
[ADD_MATERIAL:MUSCLE:MUSCLE_TEMPLATE]
[ADD_MATERIAL:EYE:EYE_TEMPLATE]
[ADD_MATERIAL:NERVE:NERVE_TEMPLATE]
[ADD_MATERIAL:BRAIN:BRAIN_TEMPLATE]
[ADD_MATERIAL:LUNG:LUNG_TEMPLATE]
[ADD_MATERIAL:HEART:HEART_TEMPLATE]
[ADD_MATERIAL:LIVER:LIVER_TEMPLATE]
[ADD_MATERIAL:GUT:GUT_TEMPLATE]
[ADD_MATERIAL:STOMACH:STOMACH_TEMPLATE]
[ADD_MATERIAL:GIZZARD:GIZZARD_TEMPLATE]
[ADD_MATERIAL:PANCREAS:PANCREAS_TEMPLATE]
[ADD_MATERIAL:SPLEEN:SPLEEN_TEMPLATE]
[ADD_MATERIAL:KIDNEY:KIDNEY_TEMPLATE]
[ADD_MATERIAL:TALLOW:TALLOW_TEMPLATE]
[ADD_MATERIAL:SOAP:SOAP_TEMPLATE]
[ADD_MATERIAL:TANNEDCHITIN:TANNED_CHITIN_TEMPLATE]
[ADD_MATERIAL:TANNEDSCALE:TANNED_SCALE_TEMPLATE]
There is of course a reason why the tanned scales and chitin are in both material plans. Titans and presumably other genned creatures, it turns out, either use these defaults or start with a base creature to modify, but when they do oddities like add scales to a mammal or create chitinous lizards, they add the required scales and/or chitin but aren't coded to add the normally non-existent materials I've added. The end result?
Whether this fix will idiotproof ALL generated creatures, I don't yet know. It should at least work for anything that starts with a mundane creature and modifies it.
Obviously in your mod's instance, pelts and other styles of hide can easily be added and adapted to the same system. The only exception is the "cleaning feathers" reaction, solely because that demands a comb instead of a scraper.