Just make Thrall Warchief again. I don't care if he's "fucked up too many times" he did a fine job as Warchief and if you just ignore his... "failings" if that's what you want to call them, but he's the founder of the current Horde and if not for him it wouldn't have even been connected as it is now. We need an Orc Warchief who's young-ish? Thrall is the perfect candidate.