So, there's two requirements for Bitcoin 2.0, or the replacement for Bitcoin 1.0
1. Eliminate wasteful mining driven by computing capacity.
2. Decentralize the currency exchange function.
#1 is easy, #2 not so...
Oh, RLY? #1 is not easy. There must be proof of work to ensure the validity of blockchain.
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.
Who sets the capacity limit? Who make a cellphone and quad 6990 rig "level". How do they do that?
Now rethink this theory uses decentralized network.
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.
Now you are just talking in circles. Neither extreme has to exist. Enough people mine so the network is strong enough. If more people mine profitability declines and some people drop out restoring equilibrium. If less people mine then profitability goes up and thus more people mine restoring equilibrium. As economic activity of the network rises scarcity drives up the price of BTC in fiat terms increasing the revenue to the miners thus encouraging more mining and stronger network.
Well, clearly then, the return to mining is an economic inefficiency that should tend to zero over the long term, that it does seems to be the consensus. Besides, the mining capacity arms race results in equilibrium being a moving target. I seriously doubt most miners who make a hardware investment for that purpose at this point in time will ever reach break even before something better to do comes along.