Thanks to stacksmashing and kbeckmann, it is now possible to load other games on Game & Watch:
• Bringing homebrew to the Game & Watch
Here is just a quick (and dirty) modification of their source, to enable loading a different game at start if there is a pressed button... (4 for directional buttons and 1 for no button)
1MB flash size wouldn't accept more. I disabled saves to have enough space.
stacksmaching channel:
/ @stacksmashing
kbeckmann channel:
/ @kbeckmann