Isolate portions of a belt for posing

Hi all,
I am working with this belt (see also blend file attached) and would like to improve it a lot.


The belt is great for precise posing because it has many bones (256) but there is room for mistakes when posing
My question : can we build a UI that would allow me to “isolate” portions of the rig (bone n to bone n+x, say bone 100 to 150 for instance) and work on that portion only without affecting the LocRotScale of the remaining bones (1 to 100 and 151 to 256). And in a perfect world, it would be nice to be able to work on FK or IK and snap FK–>IK and IK–>FK on that isolated portion.
That could be a paid work if this is technically possible.

I have tried Spline IK but I need lots of bones, posing is not that easy and this belt is more precise and gives more natural results.
Thank you guys for your advices and help
BeltRig_v005OK - copie.blend (1020 KB)