Would not work,remember the Yahg have to think you are that much powerful than them or they will actively attempt to kill you and take your place.
Eh, they could figure out a way to incorporate a yahg that doesn't fit the standard mold for the species, or otherwise have it's recruitment mission be about us establishing dominance.
Man, that always sounds dirty.
Still, just based on the technical issues that would come with having a character that big on the team, I'd rather they didn't do it.
Honestly, yahg are one of the few Milky Way races that I'm perfectly fine with not being in Andromeda at all.