I think they should focus on embedded devices, and a story as a replacement for appliances using either Windows or Windows CE.
Even in todays rather unstable state, it would work fine if it was easy to bundle it such:
- an application EXE
- boot with a readonly root file system
- read-write partition for application/user settings
- builtin watchdog to reboot when/if the system crashes
There's a shit-ton of stuff running Windows of some sort behind the scenes.
I'm sure there's also some kind of cloud application I can't quite put my finger on which would be useful, but maybe more niche. I have been known to test Win32 applications I have written against ReactOS. If it works there, it will run on every Windows version still running under the sun.
Maybe as part of a CI pipeline generating Win32 EXEs?