This observation suggests that the TI99 drives should be devices with their own PORT_DIPSETTING entry: is this something possible with the actual core? Do the "Dipswitches" and "Configuration" menu allow sub-menus?
that's something which also came to my mind. Currently I'm using dip switches for selecting emulated devices (which in reality means attaching/detaching the device), and also for configuring, representing real dip switches. Maybe there is potential for more structure in configuration, like grouping dip switches with devices, only offering them if the device is actually attached.