I disagree with the notion that Dixie would just be "the better man's Shantae". Aside from hair-twirling antics, the two have no intrinsic overlap whatsoever, either in terms of design or abilities:
Dixie is an amiable ape with prehensile hair and a pink hat. She can use her hair as a whip, carry objects with it, hang from aerial vantage points with it and whirl it around to fly like a helicopter. In terms of weaponry, she has a supersonic guitar and a toy gun that shoots bubblegum. She can summon her Animal Buddies - including a rhinoceros, parrot, swordfish and spider - to aid her in battle and team up with her fellow Kongs to enhance her capabilities.
Shantae is a sultry half-genie with magical powers. She can use her hair as a whip, but that's about it as far as hair-based tricks go; otherwise, she's more at home with her diverse range of weapons and gear, including spiked balls, storm clouds, a flintlock pistol, cutlass, broadside cannon, parachute hat, stat-boosting milk and bubble shield. Rather than summon animals, she can use her magic dances to transform into a variety of different feral forms - including a monkey, elephant, spider and harpy - at will.
Aside from the hair whip and, if you want to really stretch it, musical talent and animal elements, there's really no crossover there. It'd be incredibly shallow of Sakurai to say, "Yeah, we need a hair-based character in the roster, Dixie does that just fine." It's demeaning to bother characters and their fans, plus it just reflects badly on Sakurai and demonstrates a total lack of knowledge in these characters' individual potential.
If Dixie gets in over Shantae, it will be because her individual criteria are as good, possibly better, than Shantae, and most importantly, she is a first-party character with a prestigious and valued history with Nintendo; it won't be because we need "muh hair fighter rep".
/rant
As you were~ :3