I don't see any problems with having villians, but if they made a TvsC2, odds are they would rather add more series in them give the current ones more characters. [although I'm not sure if Tatsunoko even has enough series with characters that fit on a fighting game to make a new one, but I digress.]
I don't really have a problem with Megaman not being in, but it is weird they instead use 2 non-main character[as in, not the protagonist of their series] as representatives, and this doesn't happen with other series[can't speak for the Marvel side, here], with an argueable case with Darkstalkers, but Demitri couldn't go in mostly because of Midnight Bliss.
Anyways, Hsien-ko looks interesting. She was one of my favourites on Pocket Fighter.