I'm afraid the TRUE answer yto your question is "You Can't" unless you use DirectX directly - which gives you more control over how actual mesh and animation data is... I guess delegated...
DarkGDK has some ceilings - and many more strengths. Try bringing the polys down or something. I know what you mean though... I have some models I use only 9000 poly each - but after instancing those a few to many times... its a bit taxing.
you can clone, and you can instance. Instancing is great from trees and static stuff... or if you have a bunch of girld line dancing in unison - but not as a "smart" resource preservation tool for the application you describe here in your initial post.