I remember someone (I believe it's Jeffrey Gomez) made an animation importer for prims, but it's really just an elaborate hack to get prims moving. What I'm suggesting is the addition of a mode for prims (or a particular prim, say cylinders) that makes them act like bones in animation programs such as Poser. Properly linked, aligned, and named, they would be able to run a BVH animation uploaded to SL and played with the llStartAnimation command and stopped with llStopAnimation in the root prim. Permission would not be required to play animations on objects so long as the script making the request is in the root prim of that object.
Support for this would allow for non-humanoid appendages (tails, digitigrade legs, tentacles), more appendages (insectoids, arachnids, taur hind legs), and real jointed fingers (no 100+ prim hands just to give an "okay" or "screw you!" gesture).
(vote proposal here)