It could be done. Change the reference year every year.
For example
Base 2020's payment on the average of 2015, 16,17,18, and 19.
But divide the pot equally among everyone for 2020.
Then in 2021, take the average of the previous 5 years (20,19,18,17 and 16).
Same for 2022
If someone started for example in 2017, only use the average for the 3 years that they started in to calculate the first payment.
That way, you have to keep farming every year in order to maintain your average.
It would mean a small change in the amount that you receive every year, but it would be linked to what you did for the last 5 years instead of what your father did in 1992.
It's only a suggestion. I'm not saying it would be ideal and there are probably many holes that could be picked in it.
I'm just tired of the melody that was sung to us for the last CAP negotiations that "nobody should lose". That's bull crap! Only active farmers should be paid. Nobody should be getting money on the basis of what they did in 1992!