I also think a faster 060 accelerator would be welcomed and sell very well. So many people want to upgrade their Apollo's to 060 and Blizzard 1260's always sell quickly so there is definately a market.
I would love a 100mhz+ 060 that supports faster Memory, I think that would awesome and if such a project was viable I think it would be successful. And bolt some kind of RTG/Indivision onto that and you'd be onto a winner.
As far as I can see you have two types of user here, those who want a basic WHDLoad machine and those who have an upgrade bug who just want to push the limits of what is possible with these machines.