Well, you do have it figured out. Since this is the spoiler forum, I can tell you what you have in store if you try to be dragonborn using another race - disappointment.
You will get to the very end - the final battle. You are fully prepped after 300 hours of play. Just as the battle starts, the screen goes blank, the sound makes this odd screeching noise like fingernails on a blackboard and an image of Cicero shows up on your screen. He then goes on to give you some raspberries, say you aren't a Nord so you can't finish & then the game teakes you back to Helgen where you are knocked back to LVL1, all your possessions, skills and perks lost & you have to start again.
Now you know.
Youre really cool for acting like a complete idiot.
Obviously in the game you can be dragonborn with any race, I'm saying lore-wise. Not gameplay-wise. The only race that has any connections to Dragons are the Nords. Every dragonborn has been a Nord, every person who has learned to shout has been a Nord, its a Nord tradition, everything in the game points to the dragonborn being a nord. It sounds kind of silly to have a Altmer dragonborn.
It was different for the CoC, since there is really no information on who or what he is. He's just a guy who helped Martin, that it. But in Skyrim your are the Dragonborn, the savior of Skyrim and protector of the Nords. Nobody but the Nords understand what it really means to be the Dragonborn.
And wasn't the hero of Morrowind a reincarnation of a Dunmer general?