Minimig is Amiga specific. I don't think any other system could be emulated on it (with the exception of Atari, maybe) and I honestly think it's not necessary anyway, because it's already a successful product. Comparison with A600,
1 - Onboard scandoubler on Minimig
2 - No moving parts, no floppy hassle, breeze to download adfs from internet and play them.
3 - PC keyboard/mice compatibility
4 - small and consumes low power
and most important of all, when you're buying an A600, you're buying a 15 year old product which is near the end of her life. A simple cap leak can waste your money. MiniMig is new hardware and will serve you much longer than an A600.