All characters will have alternate costumes, of course. This is rather a case of an alternate character -- and pretty different than Wario, considering this is an actually different character rather than a radically different attire.
I wouldn't get my hopes up for a lot of similar cases, though. There are a few cases where this fits, because the Smash character's moveset can be attributed to a different character as well (as in this case, female Villager or Pokémon Trainer). But it's hard to imagine, say, Soda Popinski in Little Mac's place; it's even hard to imagine aesthetically different characters with similar movesets on each other's place, like with Captain Falcon and Ganondorf -- how would that work? Would Ganondorf crash the stage with his Blue Ganon or would Captain Falcondorf turn into Falcon? What about the different sizes and animations?
This seems to be mostly a counterpart thing -- characters that have a male/female counterpart (or something similar) will usually work. "Similar characters" like Fox/Falco/Wolf or Peach/Daisy could work, but I'm not sure -- Peach's moveset in Smash is nothing like Daisy, for example, although they fit stylistically. A similar dilemma can rise with Link; OoT Link would be great to have, but Smash Link's moveset is based on TP Link at this point, with the Bracer and the Gale Boomerang.