I think there'd be a viable* market for replacement motherboards** for classic Amiga cases.
A MiniMig II with a few active PCI slots for an A2000 case, with the USB and PS2 and video ports on breakout cables that attach to brackets on the back, or one that fits nicely into an A500 case and has extension cables that reach over to the holes for the various ports along the back and side might be nice.
...
*= a few hundred units
**= for 16 bit Amigas; the MiniMig's TG68 core is fundamentally a 68000 CPU irrespective of clock speed and might leave 030/040 users (a4000/3000) wanting.
