tx12001
I will not tolerate failure...
Actually a dragonborn emporer would be a more intimidating ruler due to their power, for instance do you think the thalmor would go against a guy who could say 3 words and cause a hurricane over the summerset isles or summon dragons to attack their landYou don't need an Imperial as Emperor. There have been Dunmer, Breton & Nord Emperors/Empress. An Altmer was in charge of the Empire after the Oblivion Crisis.
Though just because the player has the Dragonblood, doesn't mean they're fit to rule. Some of the worst Emperors known to Tamriel were Dragonblood.
as I said before the dominion would be more likely to surrender to a dragonborn over intimidation from their power other than anything else and wether your character would be fit to rule just up to the person who created them