Alzrius
The EN World kitten
Wow, I hadn't heard about this at all before casually glancing at this thread, but now I'm quite excited regarding Exp20!
The hard part isn't so much the CR system, but that monster abilities need to be refined in terms of what level adjustment they're worth. That's largely a separate concern from CR.
I've explored that, but monsters and the CR system is so ad hoc that it is tough. Not impossible, but the rules are so wide that they are only slightly helpful. But more conversation along this route is certainly possible.
The hard part isn't so much the CR system, but that monster abilities need to be refined in terms of what level adjustment they're worth. That's largely a separate concern from CR.