The theme of the version that we sell an Apple device in question comes from the factory and not open devices in stores. On the issue of being able to perform an update and not link it to an account it is not very difficult. The first would restore the device from a computer with iTunes and our Store account disabled. Then we would proceed to restore completely and during configuration iOS (the new, with their gray screens presentation) disconnected before any change. In theory there would have to synchronize any data because when the other user turns the iPad will encounter the setup wizard and start entering your data and it will end completely configured and running no data in any previous account.