"they want to give players a more "identity" choice over just "loadout" choices"
This is such a cop out. The real answer is "we want to force people to spend as much time playing as possible to hide the lack of content". It's clear as day that people are going to be switching around covenants, Blizzard just doesn't want everyone unsubbing between patches.
"players whose play style emphasizes player power"
You mean every player in the game? Isn't that the point?