This whole thing sounds awesome. The framerate issue has been one of my queries about this game in retail, now that it's that high I'm fine with it. I think shadows need to be added and like SpaceOmega said given a switch between on and off.
The .blb file idea is great! Very simple, so for that if you're hosting a server and you have like a 12 4 5 (for instance) will the clients need to spend much time downloading the blb file?