Well, since I am involved in NitrOS-9 maintenance/development it is already useful for me to be able to boot up on real hardware and run a few system tools, and to test DriveWire and other things that cannot be fully tested in an emulator. I can imagine some fun things like remote terminal server should be possible. But I don't know yet of any useful applications that fit. If "useful" is valid in this context
It should be possible to optimize NitrOS-9 to leave a bit more free space. For instance are some boot and init modules stuck in memory after booting. And of course having some of it resident on a ROM cartridge would help a lot.
In fact there was not much juggling needed, basically a one-liner change to load the boot track below 32K. It only maps memory up to the boot track anyway. I also changed the boot screen VDU location from $8000 to $0400 so that instead of watching the ROM, I can see the guts of NitrOS-9 while it is booting.
[EDIT: added disk image and updated patch]