One thing I am surprised that you suggested is to exclude lower grades. I personally will never support that. While things have been improving lately (e.g. ACT Rifle Club Applause) , F-Class has in the past been excluded from many TR only competitions and award categories so we should know how it feels to be excluded. I should add that its not a huge amount of extra work to merge A and B Grade scores.
Many years ago Alan Burkhill used to run a ranking system. It combined Queen's and OPM results, and did reflect the pointy end of the TR sport. He made the following comment relating to not including lower grades:
Only A Grade shooters are taken into consideration for inclusion in the list as it is considered that to consistently produce the scores required to be in contention a shooter must be graded A Grade. If there are shooters who are graded lower than A Grade and who are producing scores which would see them included in the list then the Captain of the Club to which that individual belongs should look at his/her performance in that role.
ATR No.8 pg66
I think it has merit.