I love MO, and have always been a big fan of 'sticking it to the man' whenever possible. That being said, as I get older I'm beginning to feel the effects of constantly cutting off my nose to spite my face.
What we have here is a wonderful, beautiful thing; an action like splitting from the network is extreme enough that it could (theoretically) compromise the site's long-term viability, opening up a position in 'the marketplace' (cringe) for a competing site on the SE-network.
Accordingly, any 'redline actions' would have to possess a probability of critical site compromise greater than (or at least equal to) the probability that separating from the SE network would compromise MO in some essential way -- off the top of my head things like extreme monetization of the site come to mind, and it doesn't seem like these new AI moderation policies are entirely detached from questions of money.
For my money, I think MO has (for some time now) had the legs necessary for walking solo and should do so as a matter of principle, to avoid having to dignify nonsense like this in the future by posting about it. But principles don't keep the lights on (in a vacuum).