I agree with the *need* to change Shadowheart who is quite suboptimally and anti-thematically built, on top of being a class that is penalized by the ease of getting advantage in combat. Shadowheart is a detriment to the party unless abusing the broken rest mechanics to cast spells at will every combat turn.
That said, I hope Larian won't make the player too much into gods. The mechanical design of each companions is arguable inextricably linked to their background story and personality. In Larian's previous game, DOS2, I believe they implemented this omnipotent functionality though. And had free use of respec and designer mercenaries to boot.