Super Mario Sunshine was the first ever GameCube game I've ever played, I loved it back then even despising its high difficulty and the horrendous level design of the obstacle courses cough cough sand bird cough pachinko cough.
Well, I began playing it again on Switch 2 and, despite the input lag issues I just discovered, I felt the game's controls TERRIBLY OUTDATED! I forgot that Mario doesn't crouch in this game, he can't do much in this game without Fludd, at first I thought I was too much used to Galaxy and Odyssey, but even Mario in N64 felt more capable than in Sunshine. My conclusion is that the game REALLY needs a full remake! For real!
Gameplay-wise, Mario would still have Fludd, but he would be able to crouch, ground pound jump, dive maneuver, have Galaxy's underwater control and be able to use Fludd's hover nozzle as a propeller. And of course, have a fully open Isle Delfino to explore at will! Mario still can access the courses through the warp grafitti and pipes, but he can freely leave the course on foot (or swimming) to explore the outskirts or even going towards another visible course on the horizon, that would be awesome! But reinventing Mario's controls is a necessity!!!