I feel classes are too closely tied to characters to just allow players to change them when recruiting the companions. Who Shadowheart could be if not a priest of Shar? It is a different system then D:OS2 which was classless - really, what set of skills our characters invested in was rather irrelevant. When/if multiclassing becomes available it should still provide some measure of customisation.
That said I wouldn’t be opposed if they created some in-game, in-lore way to respect our heroes including changing the class - one could add this to the plethora of gameplay conveniences that tadpoles provide.
Though my preferred method would be something similar to what Deadfire did - a limited choice of class selection for each companion that makes sense storywise.
