I'd rather have full 68060 compatibility (supervisor/user/mmu/fpu) even if that is less efficient. I'm assuming this isn't going to be open source so that someone else could adapt it to fit this requirement?
It sounds like they are creating a low-end variant called Phoenix to cater for the Vampire A600 that will be far more 68K-like than Apollo. I agree that getting ISA compatibility is the most important, either 68020 or 68060, before new instructions that might be great, but will be unused by classic software.
TBH if they get it working, and if they get 20 MIPS out of it in the end (on the Vampire) I will be impressed. I'm glad they have a development target too, that always helps motivate people.