Shit, did the source code for Fightin' Spirit ever come out? Imagine a bunch of dedicated Amiga guys getting together with the code for this and making a sequel or spinoff! A few tweaks here and there, maybe adding those supers and combos, a few extra effects or something. I'm sure it'd be possible, as the game ran on a 1mb A500, so there might be a bit more memory left on a 2mb A1200/CD32 to add these extras and make a new Fightin' Spirit game.
But if a sequel could be made, what could it be called? "Super Fightin' Spirit" is already used in the game (a secret mode, if you hold left on the last menu item in the game options for a few seconds). Fightin' Spirit II? Hmmm... damn I want more Amiga games!