Don’t need a new client to put Thrall on the throne in Stormwind.
If they can do events like Battle of Undercity, or that event where you bring in Onyxias head, I bet you could script a cool assault on Stormwind and put Thrall on the throne.
Hang some Horde banners in the walls.
What they probably can’t do is the whole phasing thing and keep him there.
March on Stormwind would be epic.