I must not be the first one to propose that but
would it be possible to add motion controller rotation data to any bones , not just the hand/head ?
Ipi software use great IK tech for guessing the bone rotations but it can be so much better imo.

Like the pelvis for exemple, if you try to do let's say a CatWalk or a Baladi , it's always super stiff , because it doesnt track the pelvis rotation.
Or the upper/forearm so the IK elbow pole vector have the correct rotation instead of guessing, resulting in 'ok looking' stiff arms.

Who knows , maybe even add rotation to fingers bones or even feets to improve feet floor contact/precision.