I do agree that her best appearance was from assault. But if Nintendo truly is trying to redo everything from the Zero timeline they can't leave out adventures or her backstory since denying its existence entirely would upset a lot of fans. Sure a lot of people don't miss it but it still could have been a great game not just a good/decent game. Though they could likely do the adventures portion differently, which I wouldn't mind as long as we get a good story out of the deal since she was kinda just put into the game with a wtf happened with her life/planet kind of deal and never elaborated on it(besides guesswork and fanfics).
Oh don't get me wrong, I loved Adventures and I definitely don't think Nintendo should pretend the game didn't happen.
I personally think that while I'd love to see another attempt at Adventures (to go more in-depth about Krystal's character/backstory) I think Nintendo need to focus on making something brand new while perfecting the Star Fox formula.
I've said it before that I think Assault combines the best of both worlds
- the classic arwing sections that ALL SF fans are familiar with as well as
- expanding upon the new gameplay experiences we saw in Assault such as the fresh new on-foot to vehicle missions.
Krystal has been added to the Star Fox team and has been there for almost
half of the series' total games.
Her inclusion in the series has been a choice by Nintendo themselves, it is deserved and doesn't need to be further justified.
Star Fox just needs ambition and direction, the characters have never been the problem. (Please no more tired remakes that keep the series stagnant haha..)