Shift, have you tried using the objects on different layers for render passes? Just an idea though, as I haven't used the layering system in C3d yet.
Possibly using the G-Buffer in Falcon renderer? Again, I don't know much about it other than some articles I've read about doing render passes for the z depth and then compositing and editing in another app.
I've used layers, but usually don't. The amount of interaction (and some intersection) between the different elements means it would be too complicated to get what I need - actually probably couldn't - same goes for render tags.
Hmm the g-buffer eh? I barely have an idea what that is - I think it creates a depth map. Unsure How I'd use it, but its something to think about!