No problem Zucchini, glad to try and help. It's always easier to catch things when you have an extra pair of eyes, or four, to look at something.
It looks good, though you may want to add a vermin_chitin_template to round everything out. As far as the feature bloat goes bones are a good way to brach out from this as that does mesh well with what you are doing. Thankfully you'd only need the standard bone_template in addition to possibly strong_bone (for rhinos, elephants, etc), weak_bone (for an avians hollow bones), monstrous_bone (dragon, giant, FB, ect?), and legendary (Titans, FBs?).
I'd say a good rule of thumb to follow may be if a normal person in the word could tell that the leather, fur, or material came from a very specific creature (snakeskin, dragonhide, cheeta fur) then have it be identifiable as such. In that case you just have a special_fur_template that uses the pacific animal name and that should sort out a few problems with only one type. As you said people tend to like prancing about in cool creatures skin (I'm preferential to outfitting my militia captains with bear leather (with your additions it may be fur!) or wolf leather cloaks and matching hoods. The current format you posted looks like it will have a good balance between named and generic materials so it looks good to me.
Wolf leather wouldn't be recognizable but its fur would be so given what I see you may only need two more templates: special_fur_template for distinctive furs (animal-specific of course); be it patterns, coloration, or properties (unicorn manes/fur could be used in a custom alchemical reaction by other players mods) and the presence of a carapace_vermin_template... That's only 20-21 skins right? And the potential 4 new bone templates it shouldn't be that bad outside of doing the material definitions for each. Iron and copper are good baselines to use in my experience for balancing the materials.
I was working on a boiled leather material and quilted cloth (for padded cloth/canvas armor like they had in medieval times) and it took a few tweaks to get it all working right. Mainly it's just using a quick way to run tests to make sure the aftermath looks right.
--edit: didn't see the basic carapace template... but I know crabs and lobsters have much tougher carapaces than your average beetle or spider. So the 4th carapace template still may fit.