It seems to me that companions AI will make this kind of game slower, not faster. If 10 characters are fighting and you control 4 of of them you have to wait for the others' turn. If you control only 1 of ten you have to wait much more and you are very limited in your own turn
More or less, yeah.
Also, on a side note the AI in BG1 and 2 was utter garbage and I always had it turned off by default.
