You can use your own device. You will have better hw with full root access(in Orange/Neostrada boxes you have only limited acccess to configuration of it). And in case of terminating of contract prematurely, you have to pay so called "full price"(no discounted[at least two times than street unlocked version]]) for very shifty device.
Most of them is not easy hackable and requires soldering something on M/B.