25 May 2022:
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Made a few exploratory experiments with Dragon listings - 1 REMXYZ with BASIC starting at 1E00h (7680) puts the X at 7686, which will be the starting address of the machine code if it's put there.

PRINTMEM returns 24871 on a hard reset. That's plenty of space.

Machine code is as for the 6502 with a few extra instructions (and a second accumulator, B). It might be possible to use the non-zero-page version of the 6502 code straight off the bat, recompiled to 7686. Might have to POKE it manually, though, and delete the loader when it's all finished.

https://worldofdragon.org/index.php?title=Memory_Map
Looks like 247-255 on the Direct Page (6809 equivalent of the Zero Page on the 6502) is unused. That could be very helpful.

The screen is 32 characters wide × 16 high, so it's going to be a bit of a job cramming the Illuminati's pyramid into the lo-res screen...