I think you misunderstood me. You're at the wrong end of the chain. I meant PC-ditto as an emulator to run INSIDE the STeem emulation, not as a container for a current OS.
If you can emulate a windows machine on a Falcon (or better, definitely not a ST), then maybe you can do something like:
<whatever> IN PC-ditto IN STeem IN Windows IN Atari (Falcon or better)