I disliked this feature in DOS 2, since it stripped down all the companions of of most of their identity.
I feel it would be an even poorer fit for the D&D ruleset and setting.
Not everything that is convenience for the player on the immediate distance makes a game better.
And let's be honest... The feature was in DOS 2 to compensate for the extremely low number of companions available, the mere suggestion it will be in BG3 hints at a similar problem.
As of now, my number 1 fear is an underwhelming number of companions. It's looking likely that aspect is not going to change.
Larian very clearly appears to be building their origin characters to provide a "few quality characters" instead of what I remember being much more a diverse party situation in the previous Baldur's Gates. It also appears that you're meant to "lock in" your choices by the end of Act 1 (sounds familiar... D:OS2) and then you're using that party for the rest of the game.
I want to be the focus of the campaign- my character. The rest of the party is just that- the party.
Why we need to change the class, outfit, personality, etc of these other characters boggles my mind. Instead of making an alternative Astarion, make an actual alternative to Astarion. Provide me another Rogue that I can party with. Curb their interactions to be limited and minimize VA needs. Get Jim Cummings to do a few random voice lines and make some shallow characters I don't mind losing in a fight versus the local goblins.
It simply feels like the goal is to push as far away from BG style gameplay as possible. Currently there is very little that feels reminiscent of BG.