Is it possible in unity 3.3 to use more than 2 sets of UVs, either by rewriting shaders or any other means?
Unity currently only supports up to 2 UV sets per mesh. You might be able to pull off some trickery by having two identical meshes with different UV sets and then do something with that, but it seems like any solution you could come up with going that route would be extremely complex. What are you trying to do that you need more than 2 UV sets?