It was proposed and put out for consultation to CFAs, and it was fed back that it really wasn't a good idea. Take something like a county league, or a supply league's division 1 or 2. Currently the RefsSecs know that a L5 has gone through at least two promotions, and potentially more as they could have come back down after retiring from L4, L3, L2 or even L1. Most such competitions have a rule that only L5s can referee these games with L5, L6 or L7 on the lines. That would have been impossible had such a change gone ahead.