I recently got my hands on a Pro1. Wow, what a lens. The pictures have that "bite" that only a high quality lens can offer. I'm personally of the opinion that the sun will go nova before we'll ever see a Pro2, which is a shame. With that being the case, the only option available for the Pro1 would be if Canon somehow offered a "retrofit" program. I know, I know, the odds of that happening rank right up there with the Cubs winning the World Series, but just for arguments sake, what would you like to happen if Canon did eventually offer such a thing, and how much would you pay for it?
In the spirit of keeping it real, try to limit your wish list to likely components that already exist, instead of the typical "wish list", which will push the odds back to sun-nova type thing.
Here's what I would want (and might be within the realm of possibility):
Modern NR routines
Modern movie modes (optical zoom if possible, but not the end of the world if not)
IS (if it is even possible without an enormous lens redesign)
An honest to goodness usable ISO 400 - new ISO scale (see modern NR routines)
Supposing Canon could offer that from all "off the shelf" components, would you do it for $300? $500? $200?