They didn't really need to bring Euron in to do that in the show as there's nothing that says Dany has to use the Greyjoys to return home. Euron himself, at least if they choose to actually look at the novels for once, is set up as an incredibly important villain with ties to the supernatural. Dany has dreams and visions of his coming since the second novel. Going by the books at least he should be a last "human" villain the series has before the Long Night occurs and serve as a bridge between the political and the supernatural.
That's what should happen. But then again maybe D&D want to give him the Doran treatment for ****s and giggles. Aeron Damphair at the very least seems to be getting the Hotah treatment.
