What are the limitations or design directions you would want Apollo to embrace?
Let's put it this way, I was very interested in the Vampire in the beginning when it was presented just as a speedy accelerator without any additional bells and whistles. When more and more (in my opinion unnecessary) features got added I quickly lost interest. Mainly because it seems like the aim is to achieve a vendor lock-in, hoping that developers would jump on the Apollo-bandwagon and abandon Amiga, making way for their own platform.
But as to your question, if there was a mode available that disables ALL additional stuff and mimics the 060 at 50 or 66MHz as close as possible, I would be very interested. The thing is, if I make something aimed at the 060, it runs on all 040/060 cards, UAE and hopefully Apollo Core. If I use ANY of the Apollo-features my software ONLY works on the Apollo, which for me is not good. And I know quite a few other coders feel the same way.
Maybe a 060-only mode will be available some day, who knows. But until then it's just not for me.
EDIT: And considering the core itself is still a moving platform, I wouldn't dare make any low level code on it yet and risk it not working on some later revision.