As a owner of a real 060 Amiga A1200 tower I cant say I would want one in a Minimig.
1. The chip very large and would not fit in the existing form factor.
2. The 060 has the lowest compatibility of any 68K CPU for running Amiga games and software.
3. The chip is just far to expensive even second hand.
I think the best option is to ether emulate a fit an 020 or emulate an 030 from the point of view of speed and compatibility.