I hate this idea, I think the Ironborn need the Kingsmoot and I hate the merging of Euron and Victarion. Get rid of Aeron sure, but Euron needs to be mysterious. The kingsmoot has one of his and AFFC best scenes with the horn.
I'd also hate Victarion and Euron being merged as characters (I really can't quite see how that could be done :|), but I don't see a problem with eliminating the Kingsmoot. If nothing else it stops them having to stop and explain why the family of raping, pillaging, viking pirates have a talkathon as their election mechanism for successors when all the other families
stand by male primogeniture just kill each other.
Either way Euron will become King of the Iron Isles, Victarion will be head to Essos, and Yara will end up in the North.
By having Yara off questing when Balon dies, they no longer have to deal with her or where her claim actually stands. They don't have to do any set up for the Kingsmoot, and they don't have to have one - they can just jump straight to the brothers and keep the action rolling.
Balon dies, Aeron supports Victaron in claiming the Seastone Chair (or if Aeron is removed then Victarion can simply claim it for himself outright), Euron gatecrashes their party with his ship of mutes and his dragon horn, sneers all over their claim, and scares everyone half to death so they support him instead.
From then on, everything can work as is, with Euron being generally sinister and asserting his dominance, shipping Victarion off on his voyage to keep him out of the way. Or get him dragons. Whatever. Similarly, Victarion can prove himself in battle, cause some chaos on the coasts, and find his second god on his way to Mereen.
Sure, Asha won't have 'claimed' her right to the Chair, but she would have lost anyway, and maybe this will be a better use of her time. She can stake her claim if/when she returns with Theon with one of those "This throne is
mine ours by rights!" claims that everyone loves
The book kind of suggests they'll have to rerun the Kingsmoot anyway by explicitly stating that one was declared void once before due to one of the heirs not being present to put forth his claim. Once Stannis finds out Bran and Rickon aren't dead (and there are enough people around who can tell him that) then he'll have less reasons to want Theon dead, and he could be more useful alive. If nothing else he can be a tool to shake things up over there - he wouldn't have to
win the Re-moot for it to shift the balance of power (and I doubt he could at present).
If that happened the show could always just run the second one instead, or introduce a Kingsmoot as a way to contest a ruler rather than elect one. Or skip in then too