Why? On the best day with the wind at its back, Zorro gets...what, 12mb/sec thruput? And even if you're writing drivers for the PCI bodges available for the various systems you still hit a bottleneck unless they're the ultra-rare type that hook straight in to the accelerator card.
Buffered IDE and USB 1.1 are about as powerful as you could ask for, I/O wise, for the Amiga. More drivers for the (USB) gear thats out there, that's what's needed.
Problem is folks are looking for a silver bullet to solve everything. There are two camps of users and it has to be realized that one hardware package won't fit both's needs.
Minimig is perfect for the person who wants a A500 with some possible expantions. Minimig is not for a Amiga follow on, your going to need modern hardware for that with modern OS.
Dammy