A tablet with carrier-capable hardware would be a lot more appealing if it were not restricted to one carrier. I want to have the option to easily switch carrie

A tablet with carrier-capable hardware would be a lot more appealing if it were not restricted to one carrier. I want to have the option to easily switch carriers any time after buying the tablet (or any other expensive device). An even better proposition: let me have accounts with all the major carriers, and pay for only what I use. The device should continually switch between carriers based on some combination of price and signal quality.