Yes, you read that right, we actually have PANTS.
More specifically, we have Manuel Bastioni Labs characters, with clothing proxies, which I finally managed to make deal with updates for multiple characters over multiple frames. (After much hacking and slicing and blind fumbling around in the Blender Python files.) It seems that the Bastioni Labs are currently geared heavily toward production of single images, unless I'm missing something.
But in any event, I n00b-hammered my way through, and the result is a system by which I can load a MegaMotion-exported BVH scene with an arbitrary number of actors into Blender by duplicating a single (or soon to be multiple) MBL figure, with an arbitrary number of proxy items. (Multiple proxies per actor still untested but should work.)
Every piece of clothing has to be updated in advance of every frame render, and only one figure at a time can be "the" MBL humanoid figure, so I had to write a frame handler function and loop through a pre-established list of figures and proxies. For every figure I have to call his "init" function, which is time consuming, before fitting this character's proxies.
It's not the most efficient system in the world, and I'm hoping that with more time I can optimize the system, but hey, it's not realtime - we're doing this on a render that takes a long time anyway - so who cares?
Anyway, exciting times over here! Next big step is making sure rigid body animations can be imported, so we can drop our helmet and our rifle when we get shot. After that... things are going to get interesting.