I think this feature would be implemented if the amount in kickstarted would reach a certain amount, but I think it only make sense in frame-by-frame animation, while here you can just copy the key frames and edit them.

Onion skinning a Kicstarter stretch goal which we just reached a few hours ago. It'll be a little bit of time until we implement it.

Note there is IK for posing. Click the Pose tool, drag a box to select multiple bones, drag the bones. There is no IK at runtime though.