The daisy chain board is the key and likely controls the drive select logic. I don't want to be responsible for any damage, but its likely the floppy emulator will work on a IIgs, if you connect its internal header to a Apple 3.5" drive's daisy chain board. Using a multimeter, the 3.5 Select and Drive Select lines don't seem to be directly passed through the board. Pin 4 is not wired to chassis ground either.