While the concept is solid, getting carriers to go along with this is going to be impossible I would imagine. The other issue at hand is hardware pricing, especially for US consumers.
In the US, carriers love to lock their customers in by SIM locking their subsidized hardware and customers have come to expect this low cost subsidized hardware.
If you suddenly switched to a system where hardware was sold at retail cost, there would be a lot of confusion. I am guessing that if you ask the typical US consumer if they would like to buy their iPhone at $199 and commit to a contract or pay $649 for the ability to switch to another carrier at will, they will choose the contract option. It's what they have come to expect.
This type of system seems more suited to work in countries where subscribers already purchase unlocked hardware at full retail prices.
Sure US consumers are generally ignorant about the ins and outs of subsidized hardware, and they take 2-year contracts as a matter of course. But there's no reason a lot of people wouldn't pay full price if the economics were laid bare.
For instance, when I tell my US friends that I pay £15 / month for unlimited data, 300 mins, and 3000 texts on my iPhone with tethering in the UK, it blows their minds. The fact that I can hop over to another country, buy a sim card for 10 bucks and instantly have data without having to sit on hold and beg a customer service rep to unlock my phone and then wait weeks is another huge bonus that any internationally traveling American can appreciate.
The only problem right now is that major carriers have a good thing going with overpriced contract plans and see little reason to offer reasonably priced pay as you go, thus giving Americans the impression that mobile service is inherently more expensive than it is and believing that they are getting a great deal with subsidized phones. But with globalization this illusion is bound to come crumbling down sooner or later, and customers will demand more.
In the US, carriers love to lock their customers in by SIM locking their subsidized hardware and customers have come to expect this low cost subsidized hardware.
If you suddenly switched to a system where hardware was sold at retail cost, there would be a lot of confusion. I am guessing that if you ask the typical US consumer if they would like to buy their iPhone at $199 and commit to a contract or pay $649 for the ability to switch to another carrier at will, they will choose the contract option. It's what they have come to expect.
This type of system seems more suited to work in countries where subscribers already purchase unlocked hardware at full retail prices.