Inverse Kinematics

Issue #5409 (closed) makes clear that vanilla's unorthodox actor collision on terrain will not be replicated, so unpleasantly conspicuous floaty actors compared to Morrowind are here to stay. Likewise, a move away from capsules to AABBs as part of #4247 (closed) will mean visible "snapping" of actors as they're stepped up or down, which would be something of a visual regression compared to current behavior. Inverse Kinematics with interpolation would resolve both these issues, to say nothing about being a major enhancement to actor skeletal system in its own right, and a big ticket item to more realistic animation and support for later titles.

No extra data is needed from actor skeletons; all IK is applied to appropriately named bone chains through the engine itself, as is the norm for games iirc.