You can kick and scream all you like, but it's probably not going to happen: firstly, sprites and mesh distortion are made of textured polygons, therefore there is already a way to display textured polygons as you wish. Further, the collisions algorithm would be, as I said, a tricky and time-consuming thing to program. Of course it's possible, but the collisions engine is a highly optimized and low-level MMX based bitmask generator and tester, and would be difficult to adapt. In the same time it would take to do that, we could've done several things useful to 10x as many users. Therefore, it just doesn't make sense to implement it right now.