So, Star Fox Zero is doing a carrot-and-stick routine with a fan-favorite. If Zero sells well, they will put Krystal in the next. Too bad it won't work. There are many factors that prevent the carrot-and-stick routine from working.
1) Zelda's insistence on the use of a stick. Hyrule Warriors was the fucking awesome Zelda we've wanted since 2007, and then Koei decides to add Tingle as DLC. "Pay 5 dollars to get hit on the head with a stick". The 3DS version adds a lot of Weed Whacker/Wind Breaker/Wand Wacker/whatever content. "The handheld version can hit you with a stick if it so chooses." Some imbeciles don't mind getting hit on the head with a stick, which makes things worse. As Zelda insists on using the stick, why would Star Fox bother with a carrot?
2) Star Fox is dead to Nintendo. The only reason they push out games for it, Metroid, F-Zero (trust me, they WILL bring it out to ruin it), or even Fire Emblem, is to satiate casual fans. Miyamoto is heralding a "safe era" of child-friendly games. Compare the original DKC games to DKCR (or even DK64, for that matter), for one. Nintendo seem head-on with wanting to dispose of the non-kiddy franchises.
3) Some imbeciles seem to not want a carrot. Krystal is good for you! She likes you! Why do you bash her? Worse yet are the MONSTERS who fucking worship Tingle (Nintendo's Barney). They want to be beaten with a stick until the franchise is beaten to death.
4) There's too many flaws in the game to begin with for the carrot to work.
It would have worked better if she were a pre-order bonus or accessible via an Amiibo, instead of just held on for the next (which is unlikely to happen). Instant gratification = happy customers.