Putting aside your changes to the 3 healers, you said the next healer would be a buffer/debuffer.
That just creates a brand new dichotemy of pick one shield/regen healer and the new buffer/debuffer class. It breaks everything once again (ignoring that these changes continue to make WHM the worst healer).
A legitimate WHM remake needs to make you WANT to have a WHM over AST or over a SCH. A 2 whm group to be good.

Unless WHM is just as good at ogcd healing, dps, and utility as the other 2 healers, its crap.