The fact that Larian already said the Origin characters you do not take with you after Act 1 will not be playable after you leave for Moonrise (similar to DOS2), also confirms this. Once you depart for Moonrise, you will not return to this area and you will not be able to swap out to unused Origin characters.
I really, REALLY hope they reconsider this decision. They have spent so much time writing the origin companions, I have come to care about them and enjoy their developing stories, and look forward to all their personal quests. I wouldn't want to lose them past an arbitrary point-of-no-return! Especially if they die with no good explanation
