I'm quite interested in this, but I just wanted to point out that before the events of Skyrim. Elsweyr was considered part of the Dominion, and even fought on their side. While Hammerfell became it's own nation after the White-Gold Concordat. The Dominion, now in 'legal' control of Hammerfell due to the WGC, ends up with Hammerfell fighting the Thalmor to bloody standstill which results in the Dominion in retreating from Hammerfell. Making the Redguards the only people in Tamriel to have successfully beaten the Dominion. 

Thats not to say what you've got can't work, Hammerfell is a nation that only just recovered from Thalmor occupation and a nasty civil war, while Elsweyr could easily have decided to jump ship.