Vertex alpha causes major sort issues that I don't see with regular sprites. How do you get around that one?
Add them to the surface in order of either the inverse Z-distance (this is usually faster but has some graphical side effects that go with it- minor, but they're there), or the inverse squared distance. Goes like this, add closest first, farthest last. Or maybe it was the other way around, I haven't had to write a single surface system in a while, so it left my mind.