I wonder how feasible it would be for witnesses to set reward split levels in their configurations. Then the actual division at payout could be a moving 7 day average of configs assigned to each block. That would allow for each witness to target specific levels, justify their targets, and adapt as the community adapts.
There are tons of other components that work this way (like the 3.5 day average feed price used to calculate the portion of payout going to SBD) so the technical hurdles can't be too difficult.