I've had no problem exporting Bryce terrains into Lightwave and then adding Poser characters/animation via the Poser 4/ProPack combination. As far as the number of characters, Lightwave handles groups of characters better than Poser. Right now I'm working on an animation that's a music video. I animated my guitarist, bassist, drummer, and kayboardist as separate Poser files and imported them all into Lightwave (into the same Lightwave scene file). The only restrictions I'm finding are my RAM.

Before they made me they broke the mold!
http://home.roadrunner.com/~kflach/