Splitting games for consoles without a file system (basically anything that is not on CD/DVD/floppy or DS or newer) is very annoying to do, sometimes incredibly annoying.
Most people then opt to make autoboot patches and thus force a game like that to boot a given sub game. Don't know about this specific game but it is similar enough between all games and systems (find the commands that the given menu launches the selection with and inject that somewhere that is happens automatically).
I don't know that I would give it to a beginner as a hack to do as you are going to have to get your hands dirty with assembly, and narrowing things down can be tricky (don't know if the SNES has one of those log all used functions/branches thing* like some of the NES ones). Not to mention you might not be able to jump right to it at the start of the game.
*the idea being you get somewhere in the game, start the logger, do everything but the thing you want to do and then tell it to drop everything there and note the one thing you do next (which is obviously launch the thing you want in this case).
Some come the other way and remove the options from the given selection menu screens but it is similarly tricky.
If it is only a play thing it is functionally identical, if you are hacking the game sometimes people kick the other game(s) in the head to gain the space back but that is a different matter.
Might be worth having a look for such autoboot patches too. It is a popular enough franchise and game within it that someone might have already done there.