ORIGINAL: MTK
This is incomplete.....Any propeller must turn to do any work. Prop size doesn't matter if the prop isn't being turned...
If you meant it as total work being done at maximum power by the propulsion system, perhaps! That takes into consideration not just the power system but also the load being carried. Personally I think it would be too cumbersome to go down this path. It's possible, but improbable...
Of course it's incomplete, it's just tossing an idea out there.
However if for a (very) rough example it was decided to limit 2 blade props to 22" diameter, 3-blade to 21" and 4-blade to (including contras and twins) to 20" with a minimum aspect ratio, then it would effectively cap any HP war by virtue of the noise limit.
You can only put so much power into the prop no matter the source, the total energy expended throughout the flight is still the pilot's option whether it comes from methanol, batteries or petrol.
Or they can just leave the rules alone and people can simply follow them instead of trying to change the ones they don't like.....