Then why don't make a function on sprite meshes that "rasterize" the mesh and transform it directly in a sprite? That would be easy and simple.
The whole point of the mesh is so that it has z-depth. if you want a sprite, make a sprite. It's not going to be more efficient to turn the mesh into a sprite, It will use the same amount of resources. If you really want to be able to make large textured polygon sprites (bigger than a screengrab will allow), go learn and use a 3d app.
Besides, I showed you a method for easy polygonal level creation with full support for distort map collisions the other day..
http://dl.getdropbox.com/u/1010927/DAVI ... rain98.cap