[devit]

Have you tried the approach of booting Linux and then creating a normal fullscreen qemu/KVM-based VM initialized with the memory state of the DOS OS, with a configuration so that the transition works correctly?

That would make the whole system fully robust and safe, and also support running XMS/EMS managers, DOS extenders, Windows and other bootloaders from the DOS VM.

I'm not sure however whether you would need to modify qemu to make it work and how hard that would be (also I guess that would have less hacky fun factor).