I think it is going to be hard for the professor to work that in considering how poorly Bastion went. Certainly it would be another "oops" Lacey moment, but it also should be something that would cause the MC to go ballistic. It would completely go against his character and situation to all of a sudden accept the situation, or even be "pushed" into it and if the professor does do this, I think it will be difficult for the reader to accept such conflict in the character.
I can't see an event like that happening and then it fall in line with the professor saying that Act 3 will be more of a healing progression for the MC. Any MMF event, regardless of who it is should cause the MC to spiral further, not "heal".
Though the fact that Mia isn't in the hot seat and Issac is on fair terms with the MC, I guess anything can happen in the writing.
The JD and Bastion were both huge failures and both abusive towards MC, they can't be painted as an "oopsy" moment anymore because we went already down that road.
Yes, even the JD, which was painted as emotional growth, gets framed correctly in act 2 by Dianne, as it was obvious to anyone with more than 2 working brain cells (and without sexual inadequacy fetishes), that it was a horrible moment for both of them, MC for being a cuck doormat (same as with Bastion) and Lacey for being selfish and uncaring (again).
If this happens, I would have to reconsider several things, from Lacey insisting that
she doesn't want to be shared to her whole redemption arc, which would be rendered null and void, I mean do we really want to see 2 full acts of character growth thrown in the toilet?
Hopefully, we will see some meaningful growth from MC, towards a man that keeps people accountable and gets a grip instead of fumbling around like a deer in the headlights.
I also have to agree with you that the the worst character of the novel (bar MC) is the one that seem more in the position to be selected.
I don't even want to entertain the idea that Isaac could be involved in anything or even be mentioned again in act 3 after the house is bought.