This was the first red flag for me as well. I thought I read somewhere that Beth wouldn't be adding other regions to the mix this time, but instead improve/add on to the landmass of Skyrim.
Now add that this will give issues with closed cities+ control problems, add the lore problem.
Horseback combat is plausible, however why bring up an extra house we usually get it in new areas, and the horse armor.
Sounds like someone who don't know much about the game to me.