If PP took out Henry’s heart, and put it into himself, if it worked, and PP remained himself, (unlike poor Daniel), that could actually be pretty compelling. Assuming Henry is still alive, (I know it’s been implied that he’ll have to die, but perhaps Felix just said that because PP wants the kid’s heart, and Felix assumes that will kill the kid), I assume he’d be enslaved to PP, who has his heart in his possession. They wouldn’t be able to straight up kill PP to rescue Henry, because if PP dies, so does Henry. So they’d have to figure out a way to get Henry’s heart back.