Except there IS. If he pursued a formal custody agreement she would only have access to the girls at allocated times, the purpose being that it prioritizes the kid’s lives, not hers. It would make her conform to their schedule and needs not the other way around. Every time she failed them and didn’t adhere to the agreement it could be documented and brought forth for modifications to who gets primary custody. If she decides she wants to piss off to Mexico to ride her newest dick on a whim and it’s during the time she’s supposed to have the kids then there is documented proof that they’re not a priority to her and that‘s more reason for a judge to reassess the agreement. If she wants to come back and try to bribe the kids by taking them on holiday to force the new dick on them, but it wasn’t her time to have the kids, then she can duck right off. She’d be forced to acknowledge that the world doesn’t revolve around her. But when you make sure you’re always around to cover for her when she drops the ball, all that does is tell her she can drop the ball whenever she likes. Which she has taken advantage of and does constantly. It’s classic enabling.
I’m really not sure why people think he’s helpless in this situation, he’s not. They’re divorced, he doesn’t have to indulge her manipulative, self-centered tit anymore and he owes it to the kids not to. Letting a malignant narcissist control the family dynamic is like letting a drunk drive a school bus. It’s stupid, dangerous and beyond irresponsible.