This is an amazing point. I find it hard to believe that anyone who would support banning NFEs of OU pokemon in UU play would support counting the Rotom forms as different pokemon.
We count Monferno as being the same pokemon as Infernape, so Monferno is banned from UU. Why would Rotom be given an exception from its "other forms" just because of small stat differences and one movepool difference? The original Rotom has only one move different than the other forms, just like all of the other forms. If you're going to make a "UU shouldn't be OU lite" or "they play exactly the same!" argument, Rotom should be banned from UU when these things become OU.
I'm keeping my vote of #2 because I think that they should be counted differently, with the "other forms" being OU and original Rotom being UU assuming the stats stay that way, i.e. I don't believe in banning NFEs from UU.