Changing texture import settings during runtime

I'm working on a painting game that has to copy texture files during runtime, but I'm running into problems getting everything to work as desired. After a lot of goofing around with all kinds of different copy, delete, and load functions I figured out that I need to be able to change import settings on individual textures during runtime. (OR at the very least I need to be able to enable read/write to a texture file) Also: I want to avoid a situation that enables read/write for every texture in the game, ideally I would like to only flag the files I want for read/write. Any insight?