There's a patch I remember seeing on Aminet that patched unimplemented instructions realtime to let you run 020/030 apps on the 000/010.
I tried it and it really did work! D=
How does it cope with, for example, 020+ addressing modes?
Suppose you had:
add.l (a0,d0.l*4), d1
...which, as far as I know takes up exactly the same space as the vanilla 68000:
add.l (a0, d0), d1
...is there even room in the instruction stream to replace this with a jsr to a routine that can handle the scaled index mode?