I wonder if cutting a trace near the 512k trapdoor expansion ram, like you have to do on some of the other revisions (rev 5 comes to mind) would work. Might be able to experiment and find a little known or never known A500 hack :-)
Maybe try disconnecting one of the jumpers to Gary or pulling up a certain pin. Sorry... guess it's just the tinkerer in me thinking out loud! lol
