Im not sure if this is even possible, but its it at all possible to implement the same type of credit/continue award system found in arcade console games, mainly the games by Konami and mainly Gradius 5 on the PS2. Where when you first play the game you just get given the 1 credit and each time the game ends it gives you 1 more credit up to a max of 8 i believe. I often think to myself ill limit myself to just a few credits when play games, but this never happens and you just keep continuing.
Just think it would be cool if this type of credit system could be implemented into GroovyMame to make the games have a more lasting appeal and actually force you to get better at the game, rather than just stumbling your way through because you have unlimited credits!