It's no different than what we have now?
We currently have two completely different races within the game files, "Dwarf" and "Dark Iron Dwarf". What would change isn't the number of files, but rather the location of these options on the character creation screen.
You still have "Dwarf" (though I'd specifically change their name to "Bronzebeard Dwarf") and "Dark Iron Dwarf", still treated as entirely separate races with their own textures, emotes, voice packages, racial traits, etc.; rather than being listed as two separate races on the character creation screen, however, all of these options are located under the umbrella of "Dwarf".