I would like to know if there's somekind of switch to change between Df0 and Df1 that could be done in an A1200, and a guide to do it if that's possible.
Why not take an external 3,5" floppy drive case and build it in there ?
Then take a connector just like the external DF1 connector and place it near the Joystick port 1 (warning label) on an A500 and solder a floppy cable to it and your done.
You can use the DF0 space for a harddrive or CF adapter.