With all the Shantae talk I've been seeing, I guess I'll pitch in. I've seen one detracting suggestion that she's too sexualized for the game. Note:
*While this IS fanart, it's probably not far off from what she'd look like.
We can assume that the reason Tharja's trophy got booted from the game was due to her being "too sexual" for an E10 game and that Nintendo was apparently very dedicated to maintaining that rating.
I think there's something key to note here: Shulk and Zero Suit Samus both show a lot of skin in specific palette swaps, yet it didn't drive up the rating. Palutena is apparently allowed to have panties (Sakurai bias pls) yet the game maintains it's rating.
I'm pretty sure the reason Tharja was cut has to do with Tharja being a more inherently sexualized character (in personality and attire) whereas costume design seems to be able to get away with a lot.
Hence, I don't think Shantae's design hurts her chances. But the real question is this: Would Capcom really get three representatives among third parties?