You all really shouldn’t be so worried about the character alignments. If you listen to Karlach’s audio files you will hear lots of lines where she expresses empathy. While it’s of course too early to say definitively, she sounds very much like a good aligned character.
My guess is that it will be:
Minsc - good Karlach - good Helia - good Wyll - neutral Gale - neutral Astarion - evil Shadowheart - evil Lae’zel - evil
This seems like a very decent spread, especially seeing as BG2 had a very poor selection of evil companions.
That being said, the more the merrier, so hopefully Larian is going to add a few.
I think Helia is probably neutral, and SH may move towards being neutral from evil. So two good, four neutral, and two evil. Still not good enough for me on the "good" side.