I would suggest using a community version of the game. (There are many)

They typically come with many quality of life improvements intended for people who want to revisit the game.

Pokemon Modern Emerald sounds most suitable. They add many quality of life fixes including being able to bump the experience rate.

Edit: these games came from an era where you probably only had a few games. And imagine the disappointment if you could clear the game quickly and easily. Parents would feel ripped off.