Anytime Square-Enix brings up Final Fantasy Crystal Chronicles: Remastered Edition, they trumpet the game's online play. That makes sense, as it's a feature that wasn't part of the original release. Online play is great, but fans of the game from when it first launched want to know if the local co-op feature is going to be retained. Finally it seems we have our answer.
The Playstation.com page for the game includes various tidbits of info on the game's features, and one line in particular confirms local co-op play.
Join up to three friends for online adventures, or bring everyone together around one TV for couch co-op play in your quest to save civilisation.
Now the situation could be different on the Switch, but that seems rather unlikely. If the GameCube could handle 4-player local co-op, there should be no reason the Switch can't do it as well.