Why such stupid limitations?
I remember playing Paladin in BG2 and I could recruit all evil companions without ever falling or doing evil.
Yeah, they might b*** and moan and there would be friction and you could boot them out. They might even leave EVENTUALLY unless you convinced them to stay. One of them (the dwarf Korogan IIRC) would even challenge you to a fight for party leadership.

But at no point was the player blocked from having a companion in my party because I refused to slaughter a bunch of people I never met.