Shantae is a decent argument, and I won't pretend she's not a better pick. Personally, I agree on Quote as well - he's practically the grandfather of the Indie movement, his game being the first big one anyone remembers.
If Shovel Knight gets in over these two, then it confirms one thing in my mind: of all the factors around choosing characters, it's marketing that will have won the day. Neither Shantae nor Quote are as well known among the
casual Indie community (Quote, in particular, is rather dated by now). What's notable for SK is 1) he's accessible, having a very simple and intuitive moveset; 2) he's well-known and currently relevant, having been exposed on all platforms of Indie consumers; and 3) every other platform out there has unique content for SK, leaving Nintendo the only current platform that hasn't given him special treatment. Time and again we've seen the arguments that these things don't matter to Nintendo, or that console exclusivity is more important - but those are assumptions which we might soon find are to be proven wrong.
Keep in mind he would not be the first Smash character to have only appeared in a single, recent game.
The problem isn't in the characters' importance; it's in their ease of rights obtainment. Any big AAA company will likely him and haw and whittle Nintendo down for as much profit as they can gain out of them. They're already well-established brands in their own right, and that doesn't come cheap.
Indie characters are a whole other thing altogether. Indie devs would kill to have their character in Smash, and are therefore likely MUCH easier to negotiate with. By comparison, they'd practically give their characters away to be in Smash.
I don't think SK's inclusion hurts Rayman or Spyro's chances, though (in fact, Spyro's chances have actually risen with Nintendo forking over rights to Bowser and Donkey Kong as Skylander/amiibo hybrids. It's only natural that we'd soon see a Spyro hybrid amongst the Smash line as well).
Based on
our ballots, taken by a subset of fans who actually use various forums. This leaves out fans who only cared to take the Nintendo ballot. Results may vary.
If Nintendo owned SK, you know for sure his sales would be way, way better than they are. Even if the game hadn't changed at all, having Nintendo's brand on the title would add a lot of credibility, and therefore sellability, to the game. This isn't really a fair comparison.