Jim's draft proposal is well thought out, and, should an ABC list be something we need, it would do the job. Some discussion would undoubtedly ensue concerning the numbers employed to separate A from B from C, but these are details easily handled.
The main question is whether it is worth doing at all. The information contained in the new list would not be new - it already exists and is accessible. Moreover, it is not a one-time effort. The list would require periodic effort to update it. This would become a new job for someone in RRTC.
Considering that it is not hard to get measurer information at present, including courses measured and when this was done, the end-purpose of the grading scheme remains unclear.