Along the lines of option 3 for me.
20 meeting rolling avearage.
+1% for each of one at HL
= for each at 2nd string
-1% for each at reserve
The biggest downside is it could penaluse to very top scorers. Someone on a current 9 fro HL would go to 11.8.
If you wanted to alleviate this you could use a gap closure calculation. So the closer a rider is to 12 the smaller their increase would be.