Now that we have to complete list of launch subclasses, I'm wondering what would be the natural/Canon subclass for each companion. I personally try to develop my characters to fit their personality/backstory as best I can on my first playthrough.

Couple of Caveats:
  • Shadowheart and Wyll already have theirs at lvl 1, so no need to pick theirs. (However, I will say that Wyll's pact boon would likely be blade, surprising no one)
  • I don't know Minsc and Jaheira well enough to guess theirs, but since we'll likely get them past level 3 their subclass should be set.

Gale: Transmutation... This one is difficult as Gale really just comes off as an all around wizard. Going into my first EA playthrough I made him an evoker, which still fits, almost purely based on his character art (not the best reasoning), but some of what he's done with/for Mystra sounds more like Transmutation to me.
Astarion: Thief... Although assassin could also fit, I just picture him prowling the streets at night to bring home food more fitting for a thief. I mean he isn't allowed to kill them himself lol.
Lae'Zel: Battle Master... Another hard one as all three fit relatively well. Eldritch Knight works as she already gets a bit of magic as a Gith, my personal visual of EKs are a bit more nerdy/studious in personality. Champion always works, it just the fightery-est fighter. I simply land at Battle Master to reflect some of the training she has, but all do fit.
Karach: Wild Magic... Based on her brief appearance in EA along with the snippet from the community update, I think the "unholy machine" she got from Hell could trigger wild magic surges.
Halsin: Circle of Moon... Before we even meet him, several other druids are referring to him as "The Bear", I.E. his preferred wildshape. Then when we do meet him he spends he entire encounter in his bear form.
Minthara: Oath of Vengeance... Obviously everything is subject to change in version 1.0, but she literally uses an oath of vengeance ability.

Obviously, the game is open enough to make any of the choices make enough sense to not break immersion so all are valid choices. I also know that nothing says you have to RP to the theme of your subclass, so I'm not saying anyone should take these as the right choices. I'm more just stating my thoughts and hope to get some feedback to confirm/alter my own narrative choices.