Went ahead and did the fletchings from feathers workaround as the yen for being able to make use of all the random unbutcherable birds (keas!) outweighed other concerns (like fear of entering the rabbit hole of my own modding ignorance).
[EXTRA_BUTCHER_OBJECT:BY_CATEGORY:GIZZARD] <--- left as is, as there was always a BP category error
[EBO_ITEM:TOOL:ITEM_TOOL_FEATHER:INORGANIC:FEATHER_SMALL] <--- forehead up against the limit of item tokens
[EBO_SHAPE:FEATHERS] <--- EDIT: noticed this line is unnecessary >_>
It was ugly and heavyhanded with both MATERIAL_TEMPLATE:FEATHER_TEMPLATE and INORGANIC:FEATHER_SMALL getting REACTION_CLASS:FLETCHING which opened up an infinite reagent exploit.
Also had to use a strange naming sequence as FEATHER_SMALL's name was "feather" for both noun and adj, and because this was the material type, it became the adjective to the name of the tool, which (at this moment at least) was "quills" and to the name of the bowyering product "fletching."
So anytime a hunter/ranger kills a small bird of at least 1700 size, besides 2 units of meat/fat, 1 unit of skin, they'll also get feather quills.
Presuming non-use of the reaction class exploit, each small bird can make 10 (material type) fletchings = 10 arrows or 10 bolts.
Probably the best way to have an Adv Mode character scratch the groundskeeper/gameskeeper/huntsperson itch.