Feathers should be dropped by mages as well. Maybe even a new alchemical ingredient that can be bought from alchemists. That way you add more ingredients for the alchemists to use, and a new item that is beneficial in crafting. You should also be able to deconstruct other arrow types to collect the feathers. a.k.a. taking crappy iron arrows, peeling the feathers off, then gluing them back onto arrows with ebony tips or whatever. I just had another great idea... Metals that are usable for alchemical purposes. :D