It's good idea, but this cannot be done in the nearest future. The price of electricity and of the mining equipment are the things that make cryptos more "linked to the real world" than US Dollar or Euro are. Mining dictates the price of cryptos. Miners won't sell their precious ETH of BTC cheaper than it costed for them to get those coins.
Exactly same thing happened to USD or most of the national currencies that we have today - on early stages, every bill was promised to be exchanged to gold equivalent. Governments promised that, so people believed in these pieces of paper. This made the bills valuable, nothing else.
But later on, people forgot about this and the mass adoption replaced the need in some strong promise. Same thing will happen with cryptos one day. Miners won't be needed to provide physical linkage to some real-life values.