This is just for fun. While I'm Ok with the companions so far, I think it might be fun to talk about the NPCs we would like as companions (not necesarily as origins, just companions).
I'll start with Halsin. A druid that can turn into a bear sounds like fun. Also, I like his backstory. Since he joins the camp, it won't be so complicated for him to join you. Also, having a divine spellcaster, would offer an alternative to Shadowheart.
I also like Karlach, which is lucky, since it seems she might be a companion in the future. I hope she is an explorer or something similar, since having another character with hide skill would offer an alternative to Astarion in case we need/want that. Alternatively, a paladin or barbarian could work as an alternative to laezel.
While I like Mintara as it is (not joinable) and don't care much for the zentarim. I guess they could work. I do see potential on the guy we rescue from the fire, the drows turned into stone in the underdark, one of Ethel's victims if saved, one of the tieflins refugees (people seem to like the bard, but I would probably like better zorru, for the tension with Laezel). I guess even the gnome you rescue in the windmill could become a companion.
So, who would want people see as companions?