Sure something like that is probably possible. Many details would need to be worked out in terms of design and math (and then coding) of course. And it won't happen any time soon (due to development resources, schedule, etc.)

One thing that may be considered at some point (not in the next hard fork) is routing the reward pool through SPS, so stakeholders have to vote to approve a proposal that funds the pool at a given budget. If that budget seems too high or too low (which of course is unavoidably subjective to a large extent) it can be changed with another vote.

From a math perspective, that may be easier than trying to redesign the reward pool mechanism itself.