It should be possible to change the default core for the entire emulator, not just the selected game.

[ruaxbk]

here is an option for "Game core" but none for "Emulator core".

When deciding on which core to use for launching a game, the order of precedence would be:
Game core > Emulator core > Default core.

[adamcroxton]

Would love to see this. A per game and a per console core option. I generally use the default and have little issues. If a game isn't running right I will just change it. But it would be very convenient none the less.

[oherau]

So far you can do this by modifying the launch.sh script of the system you want to modify.
Remember to make a backup just in case you want to revert it.