I have a very similar idea, but much prefer to peg generation and destruction rates to difficulty growth rather than market prices.

My issue with pegging generation/destruction to market prices is that it requires a third party to supply accurate price information to the system forever. Two issues with this:
a) this is very centralized; take out the third party and you take out the coin
b) the third party could benefit from supplying inaccurate information.

An ostensibly attractive option is to allow users to vote on prices, but this does create incentives to supply truthful information. A voting system can ensure that everyone supplies similar information, but it cannot ensure that this information is truthful. There is no apparent economic reason why people will form a consensus around the truth instead of forming a consensus around a lie.

Pegging generation and destruction to difficulty growth (for example to achieve 50% annual difficulty growth) does not require the supply of outside price information. The relevant information is in the blockchain already. Linking coin generation and destruction to difficulty would ensure that the coin price approximately tracks the electricity price (I am assuming Moore's law will continue to hold).

There are certain features of this idea which would make it very difficult for anyone to profitably manipulate difficulty, but I don't want to go into the details because most people have short attention spans.