That doesn't mean they can't be useful, and they do already have a chip on their shoulder wrt Iran because of Iran's support for the Houthis.
well with all the oil money, saudis and UAE don't even have to send their own citizens:
they can just pay gurkha mercenaries for the job
Yemen situation is just good indication of how useful they could be, and answer is not much. They don't have good functioning military.