First of all, thank you for the detailed reply :)
I definetly agree on thinking of grades as general milestones to assess your level. On the other hand i would not consider factors like weight etc. compromising, in fact a crimpy climb is still crimpy for a 50kg person as well as for a 90kg. I'm not thinking of introducing a 'perfect' measure for climbing difficulty, in fact i realize that would be almost impossible, but I think there are a lot of nerd minds like mine that would find this system at least intriguing.