Good thinking inside the Bitcoin Box there. If all you have is a hammer, everything looks like cryptography.

Why not a capacity-based mining metric as used in the distributed project software BOINC? "Earnings" are based on your percentage of commitment of a benchmarked resource as well as total capacity contributed. If capacity is really not needed in the aggregate, you could level the playing field between the cell phone processor used at 99% and the energy-wasting dedicated red hot pig breath generator running at 99% or for that matter dial in any skewing of reward you might want to achieve.

The whole weird hack of the difficulty level makes it clear whats really going on. Set it to minimum and rework the mining block creation rate meter, which could be amenable to something as simple as a consensus-based peer to peer counter.

Right now the mining hack is a lovely illustration of the fallacy of composition. The more it's done the less is the return to each participant for their investment. At the other end, where everyone recognizes pointlessly compute-intensive mining just costs everyone more individually so that no one should do it, bitcoins aren't created. It's a truly ludicrous situation.