Actually, from Zorlun's latest posts, it seems
that indeed Myriam will go for legal guardian (and hopefully, get it). This was also one way some suggested in the past as way to get around the fact of Anthony and Myriam not being a couple on the official Patreon route (remembering originally they were married and Marc and Katherine were their kids).
Adopting would probably not work for Patreon, it seemed they had told to Zorlun any kind of family relationship, even "step something" was off limits - so, by logic, even adoption should be off, although Patreon's logic is their logic, so can be different
.
If Myriam was to become legal guardian in the Patreon version, than it should be relatively easy on the incest patch version to put it as a battle for custody of children, as happen in many divorces and separations, and keep (as is already, and was in the original), Myriam and Marc as mother and son.
About your reference to Katherine, lesbian and the pool scene, I don't know when you starte to follow the game, but I remember that pool scene was before Patreon's intervention, so, normally yes, you would be right, but, at least to me, it is not clear how much you can count on that, or in general on Katherine having any sexual interaction.
I for one (but again, it is only my opinion), I am counting on none, and being happy if some scene happens - I understand Zorlun has alreayd a lot of work to keep track of all the possibilities, develop them, and keep everybody happy.