I see mileage in just using BFTA graded events for your BFTA score. This eliminates regional variation in competitor strength & course difficulty.
Regions could then either use the BFTA process as their regional grade or come up with their own system.
Maybe, over time, a novel regional grading system could prove itself to be a better alternative and be adopted as the national system.
Right now, I don't see a clamour to change from % based on best score of the day.