It’s my take on modular rigging. Snap Constraints ( Snap Constraints (FK to IK and Space Switching) ) was a small part of that addon. I made that one free due to the limitation of visual keying not working if the bone being keyed had more than one constraint. The new one solves that problem, atleast for rigs made up of CopyLoc/Rot/Scale/Xform, Childof, IK, Track/Damp/LockedTrackto and stretchto. The core idea is the ability to activate a rig without losing your keyed poses and without having to bake every frame. It’s the idea of using the right rig for the particular motion you want. In some situations, you may temporarily switch to IK since its easier to pose with then switch to FK because it interpolates more naturally. Instead of it being IK vs FK, it’d be more generalized to rigA vs rigB.
I haven’t tried it yet, but https://twitter.com/Wardl_/status/1264636279720984578 has a similar mindset.