Barcus would be a cool companion, but I question whether the necessary response to 'the evil companions are too snarky' is that we need three new companions exclusive to good players, because Barcus is already unavailable as a camp companion/dies if you side with Minthara or Nere, and Sven implied that Minsc and Jaheria would only aid good players, plus the stuff with Wyll, Shadowheart and Gale. The evil party members might be abrasive, but they don't ditch you if you choose to play nice.
I agree with you, having Barcus as a companion should not be exclusive to "good" players. It would even make sense for him to join our party even if he disagrees with our character's actions, since his primary goal is to free Wulbren, and he could definitely use some support to get to Moonrise Towers.
