I wasn't arguing for "the other system", that train's already left the station ( and we are not supposed to mention it
). I agree that "the other system" requires even more babysitting if you want to have complete and accurate control of your party in combat encounters with optimal efficiency, and superior results. But that's the point, I don't care about about that; I care about getting through encounters rapidly, because I don't find the actual mechanical combat particularly interesting in any game.
BG3 already has AI that understands combat for all the enemy entites, and it already has per-character configurable AI for reactions ( which is, in itself, going to give you non-optimal outcomes ) for party members, so it does not seem a stretch to allow players the OPTION to put any party character under AI control, preferably using configurable preferences as with the existing BG3 reaction system ( or something like DA:O which allowed you to specify party member combat preferences ).
In fact, the effect is no different than playing BG3 in multiplayer, where you control only one character, and can request other players to do things, but can't guarantee their behaviour.