First, NV was NOT developed by Bethesda. Second, NV svcked big. Third, who would you disguise yourself as?
First, even though this point is almost entirely irrelevant, NV used the same engine as FO3 and Oblivion, which
were developed by Bethesda.
Second, unless this mechanic somehow affected that opinion of yours, this point is irrelevant.
Third, the Dark Brotherhood, remnants of the Imperial Legion, whatever guard uniforms aome cities might have, etc. I mean, if you've played an ES game, you know there are plenty of factions you could pretend to be a part of.