I’m thinking for sintel they used a low-poly generic mesh for much of the initial stuff. I remember for a community animation sprint, they had a low-poly mesh with the same armature that sintel & other characters had. You could do this as well, create a low-poly character and rig it with the same armature the real character has. Then when you link in the character, turn off visibility/renderbility of the real character and work with the low-poly character. Once the real character is done, turn off visibilty/renderbility of the low-poly character and enable the real character and it’ll work just fine. Of course, you must have the armature that you are planning on using on the real character finished before you create the low-poly character and use that armature when creating the actions.
I think this workflow is how all professional 3d cgi work is done. You work with low-poly characters when animating, so viewport viewing of the animation is fast, and test renders of the animation are done fast as well, then for final rendering the hi-poly character is used. I just completed a project where I did much the same thing, but in my case, the low-poly character was the same as the final character, just without materials. This allowed me to render the animation in about 2 hours for preview purposes. After adding materials, the final render took over 36 hours with 3 networked computers as a renderfarm.