(I imagine that he would have claimed Bael and the authority that comes with it eventually in any case, but only after he'd already established firm control over Gjallarhorn. It would have been a capstone, a symbolic nicety cementing what he had already achieved through diplomacy and backstabbing.)
I'm not sure I would call it a Hail Mary exactly, because yeah, he would have claimed it anyway and his belief in Bael as the ultimate representation of all that he desires is extremely genuine, but it is very true that Gaelio being alive accelerates his plans and pushes him into his delusions
faster than he would have fallen for them originally. He believes in Bael quite genuinely, but he's a more rational and patient person when he isn't already cornered. The more you push him the more he just loses himself to his wilder beliefs.
I've resisted the view that the delusional man-child is McGillis's true self, with everything else just being an act he puts on to dress it up, but I think I can get behind this view. He has good reasons for his actions, he makes rational plans, but when they fall short he retreats into fantasy...
Yeah, that is exactly how I see him. The trauma-based childishness is something underlying at his core that defines him and that informs all his actions, but that doesn't mean he isn't also a capable adult who's clearly made it in the world with a lot of cunning and genuine know-how.
His weakness isn't that he is incapable of logic, his weakness is that he falls back on something deeper and more primal when put under stress. As he himself puts it. "To grasp a person's heart and control their future actions is easy: unveil their past.
Just doing that makes it easy to predict their choices. And that also goes for me." He's self-aware about the matter.
...because that's what's kept him going in the past. He takes his best shot and insists that it will absolutely, definitely work, because if he can't believe that then he has nothing. It's less the true delusional self coming to the fore and more an extreme case of fake it 'til you make it.
YEP! "If he can't believe that then he has nothing" is EXACTLY it. Ultimately all the childish beliefs keep being the underpinnings of his more adult self because they are the foundation he's built on just in order to keep living.