Playing New Leaf again today made me wonder if Villager will be customizable at all. I don't think it's likely, but it would be cool if we could use different clothing/hair/etc. It is a bit possible, since none of the playable characters in Brawl were characters that could be customized. If it worked this way, I don't know if you would upload an already made character in New Leaf (or maybe even another Animal Crossing game), or if you would have to do it all in the Smash game.
This would be different than costumes in that you'd have more than seven different character models (forget if it was seven, something around that). If you could upload a character from an Animal Crossing game to use, I wonder if the Villager would need a female variant. I can't exactly imagine the game excluding female players from using their characters.