It is possible to get more clans, but it could also be a “too many cooks in the kitchen” scenario. Plus, a lot of clans are known from just taking power from others for the sake of growing their own empire or for being on the top. Any clan that would join needs to be part of a pre-expansion scenario. Especially if each clan is going to have any customization specific to said clan in some way. Plus, what to do with the different leaders to keep the clans in check? As I mentioned, if it fits the narrative, the more the better.
One thing I will say is that the Stonemaul have had enough with corrupt clan leaders, so measures would be taken to make sure it never happens again. Thus, I would not want any Ogre clan leader to turn against the Horde after joining it. Consider it a checks and balance thing, where if someone tries something, they’ll just get ganged up on and killed. Not like they’re going to get anywhere, anyway.
Speaking of which, clan leaders! Tharg is the obvious Stonemaul leader, and serves as the main leader/Ogre representation. In my scenario, he put Draz’Zilb in charge of the Gordunni. The problem is…Dunemaul don’t really have their own clan leader, and I don’t think the Draenor Ogres that left with the Mag’Har have one either.
The Dunemaul leader can just be as easy as Megs appointing a Dunemaul Ogre she trusts to be loyal and one she can have some sway over. As for the Draenor Ogres, unless I am missing someone, a new leader would have to be created and represented, along with the new Dunemaul leader, during the Dire Maul portion of the second scenario I made up. Since they really need a home and food, they would be loyal to the Horde, and the leader would be humble and working to prove their clan.
So what to do once the Ogres join the Horde with four clan leaders? In this case, I assume that an Ogre council would work fine. It’d be similar to the Dwarf council, though Tharg would be considered the “leader” or the one who represents the Ogres as a whole. It fits the “checks and balances” aspect I mentioned, as Tharg would want to prevent anything happening like with the Stonemaul ever again.
Not perfect, but it works, in my opinion!