Remove: Guile, Glenn, Leah.
Replace: Magus, Frog, Ayla.

Really, though, I'd eliminate Korcha, Poshul, Luccia, Razzly, Zappa, Orcha, Macha, Leena, Miki, Janice, Draggy, Starky, Lucky Dan, Turnip, Neo Fio, Greco, Skelly, Funguy, Irenes, Mel, Leah, Van, Sneff, Steena, Doc, Grobyc, Pierre, Orlha, and Pip. Not that there's anything wrong with some of those characters, but they just didn't have any business joining the playable cast, and taking them out still leaves a good fifteen characters, which is still a huge cast for an RPG of this kind.

And I wouldn't replace any of them with anyone from Chrono Trigger because 44 playable Chrono Trigger characters would be just as bad as 44 playable Chrono Cross characters.