Emulating an MMU is a non-issue for MacOS so it's perfectly fair to note that even a fairly wimpy PC will run it far, far faster (on the order of hundreds of time faster, for certain tasks) than any Coldfire or 68060 box will be able to. If an MMU were actually vital for running Atari, Amiga, *or* MacOS software then I'm sure someone would be able to get JIT+MMU working together. It's just not a burning issue for anyone not running Linux or BSD, which is the vast majority of the users of these emulators.
(After all, if you want to run Linux or BSD why not just run it on the host? There's nothing particularly special about NetBSD on a Mac or Amiga other than the fact it runs on a Mac or Amiga.)
As an aside, I actually did stumble across a foreign site which had a collection of benchmarks comparing various "real" Atari computers to ARAnyM, and one of the things listed was a Coldfire demo board. It's interesting to note that the 200Mhz Coldfire barely beat the 100Mhz 68060. So... more reason to regard the whole enterprise as pointless?