Subdividing bone = create additional vertex groups and bone weight options

Now: Subdivide a bone, one bone has a vertex group assigned to it the other does not, that one bone has weight paint the other does not.

New: Subdivide a bone, if the subdivided bone has a vertex group both bones have a vertex group assigned to it (option) , both bones have the same bone weight or shared half each (option).

Example: A bend is a bit stiff so you subdivide the bones, immediately solves the stiffness problem, vertex group is added and everything is weight paint properly. At most you would tweak smoothing. Done.