I have to say that a renegade Ilithid working with a (possibly renegade) githzerai out of a common desire for revenge is ... well it's a bit gonzo, but it's pretty cool too.
In other news, I could have sworn that the githzerai's stats had been published already... am I wrong?
Yeah, I'm looking forward to coming up with tortuous ways to treat the renegades once they are over their heads, possibly using some of the bizarre flying ships (nautiloids), augmented monster thralls, and other illithid magic items mentioned in Volo's.
As far as I know the Githzerai have only been statted in the MM as NPCs, though I have no doubt others have home-brewed them.