Um.. The Carriers already do this! Within 2 days of your Contract ENDING, they will unlock your phone
U.S. Wireless Carriers Agree To Make Unlocking Your Cell Phone Easier
But you cannot just take any phone and unlock it and it will work with whomever you want.. They only come with specific bands that you can't just add or remove..
however, the IPHONE 5S is already compatible with all the major carriers...
Iphone 5s from AT&T/TMOBILE is 100% Compatible with ATT/TMOBILE and all Canadian Carriers and LTE/VOLTE only on Verizon.. the Verizon IPHONE 5S/5C is 100% compatible with ALL CARRIERS including Canada except SPRINT and sprint... is all alone
The Hope with LTE and VOLTE is that in the future, You won't need to go to Verizon or AT&T or SPRINT To buy a cell phone! With Verizon and SPRINT Both planning on Dropping CDMA! In the Future, you will go to best buy and see PHONES... You won't go to the Verizon section or AT&T Section, you will just see a clutter of phones, pick one and then the carrier...