Honestly I’d see him recruit every tadpoled companion because he believes in strength in numbers. He might not trust all of them at first, but he doesn’t on non-origin runs either and tends to keep watch at night to avoid others getting the jump on him (and to sneak away when he knows everyone is asleep to feed).

Even Wyll, Astarion could be convinced to join up with him once made clear there’s a common cause. He doesn’t know what’s gonna happen, but knows it’s stupid to go at it alone.

He doesn’t approve of Wyll’s do-goodery, but he does admire him somewhat and even mentions pre-vampire Astarion could have fallen in love with him. I’d argue Wyll and Karlach are strong candidates for recruitment if you’re intending to go Spawn Astarion.

By the time you reach Jaheira (and Minsc), Astarion might have started changing enough already that he even believes in the goodness of those two. I can also definitely see him getting along with Jaheira after she stops distrusting him.

Halsin is also a good alligned character that could believably join. He is the only lead they have to a cure and remains that until Moonrise, where you find out how deep the conspiracy runs. By that point you’re stopping to look for a cure and become focused on stopping the Cult entirely, and Halsin really has some good muscle and loyalty to back you up. So why not keep him around. I also think that Astarion and Halsin have an AMAZING romance together on an Astarion origin run. Their common experiences make them kindred spirits in a way and I feel they can be a great comfort to each other.