Thaddeus Dryja's "proof of idle" idea hasn't been getting enough attention. See https://www.youtube.com/watch?v=QN2TPeQ9mnA
The idea is to get paid NOT to mine, because it is economically rational for everybody to keep the difficulty lower rather than higher (everybody saves money on electricity if everybody can somehow agree to keep their equipment idle). Thaddeus figured out a way of solving the coordination problem so nobody can lie about how much mining power they have or profit from cheating and running miners that they promised to keep idle.
Having lots of idle mining capacity is appealing for at least two reasons -- it is more energy efficient, and if an attack of some kind is detected it could be brought online instead of kept idle to help fight the attack.
However... I suspect that taking that idle mining power, pointing it to a big mining pool, and then performing a winning-share-withholding-attack (if you find a share that satisfies full network difficulty, don't submit it to the pool -- just throw it away and pretend it never happened) could be a way of doubling your profits, because you drive down difficulty, get paid for "idle" capacity, AND get a share of the profits from the mining pool you're attacking.