I'm not a fan of this choice but it's one I could potentially learn to live with. The idea of new companions coming into the game later is cool in theory but I do understand why Larian wouldn't want to go that route; the later they come in the harder it is for them to be given equal depth to the characters that came early. But if they're going to give us a limited party size then this definitely has the potential to turn out badly. If they allow companions to leave you for choices you make then with a limited party that could be crippling and would severely hamstring roleplaying because we just couldn't afford to lose out on a companion. And sure we could replace them with a mercenary, they said that would be an option, but it's absolutely a sucky option to replace a fully fleshed out companion with a silent, empty husk. I think the best compromise would be that some companions leave but you can still have a couple remain with you after that that you can sub in.