User-generated animation.

This has been on my mind for some time now, so any ideas/opinions on how to go about implementing it?
My guess is that first id have to make robust IK rig inside Unity and than add a system for users to manipulate the controllers, maybe something spline based or similar to C4D’s Cmotion and after that figure out how to save that and play it back…

Something like Unity Asset Store - The Best Assets for Game Making from Partel Lang