ability to turn off skins

Unfortunately that's not going to happen. Skins are not just a texture, they are separate models, and doing this would mean loading both a chosen skin and the base skin when you start a match. Riot wants to keep those loading times down, so they only load one model per champion right now.

It would be cool if we could force the base skins, because some people have trouble seeing abilities from some skins, but I don't think it's likely.