A.Russell's method will only work in environemnts with low poly counts. It's hard to imagine the hit on your speed duplicating your entire environments.

Vent's right about Max having lightmaps which are not connected, and possibly higher verts than the original texture. If anyone has the knowledge to write such a lightmapping tool which would work with these lightmaps, i'd be willing too pay for it. Send a PM if you have the knowledge to go about such a task. Since I know very little about d3d, and writing a plugin(nevermind the time investment) myself. Infact, I bet theres more than a few users who'd be willing to pay for such a tool. Afterall, as more and more users become experienced and use models for their levels, the lightmapping need will be even more apparent.