@Acill
The main problem with the older busters was that they didn't work as good
in an A4000 as they did in the A3000. Something to with the A4000 demanding
better signal quality or draining more current from these signal lines.
So your experience does not help here.
Bout the Mediator being PCI-solution, all three possibilties have problems
so big that non of them could be advised with a clear mind.
My advice (specially for those that are still 68k-only):
Keep your miggy "real" (only Zorro).
Use (Win)UAE, will give you all a 68k-miggy can (and since lately even W3D-compatible).
Make a clean cut and buy a Pegasos (or that other board which I can't rememberatm :-P ).