IDK if I would feel comfortable using a mobile device as a cold wallet. I think simply speaking mobile devices are too volatile and susceptible to crashing to be good enough to serve as a cold wallet. From what I can see from the OP it looks like if the screen of your cold wallet were to be cracked to the point that a camera cannot read a QR code displayed on it then you would not be able to sign transactions with it (I guess you could technically sign them, but you would have no way of getting the TX onto the network without connecting it to the internet). Another concern is how frequent it is that people will steal phones, and the number of reasons people have to steal your phone. If someone were to steal your cold wallet phone then you would essentially lose your private keys, regardless if the thief is able to steal your money or not.