At least a Rat race isn't as bad as another recent suggestion that there should be a dragon/human race that was exactly like Mass Effects Krogon. Not similar, but exacly alike.
That particular persons reasoning. Dragon Born = completely new race.
I remember that. And poster asked for removing Imperials to include that. And thought that "Dovahkiin" was a race and we couldn't play as any other race...
I woulkd lke if they added some breeds of Khajiits and Argonians, as they fit the Lore. 4 of each kind, for example, so we can have 4 Men races (Imperials, Nords, Bretons and Redguards), 4 Mer races (Bosmer, Altmer, Dunmer and Orsimer), 4 Khajiit sub-races and 4 Argonian sub-races.
Maybeif they did a TES on another continent where they create a few new races we've never heard of, but not in skyrim. I'm not a lore expert by anymeans, so I'm not sure if the whole world is as fleshed out. If it's not then adding new races could be easily done on different continents.
Well, races of other continents appear in the Lore as well. Though we have no idea of how some of them could be.