So I want to make my custom collision system into it's own library that would allow anyone to add non Axis-Aligned shapes into Minecraft. Ideally, I'd want it to work the way adding a library works because if 2 mods add the same library it only loads 1 instance of that library. This custom collision mod/library needs ASM to work though, so would it even run if I tried making it into a library?

Well you create the library like you create any other library? you tell eclipse to export as jar and make a guide thats tells ppl how to use it