Just a wild guess, but who ever created the new MiniMig core file might have been modifying the older original core that did not support the AF ROMs without the keyfile.
You do know that you can get a ROM file that does not need the keyfile buy ripping it from a running AF emulation with one of several programs available on aminet, don't you?
Hope this helps.
Edit: I see Darrin beat me to the answer.
