That would, I expect, help with the unfortunately old kernel version and generally give greater confidence in what's running on the second computer inside the computer.
That isn't wholesale, it only replaces the OS on the ARM processor of the modem, the OS on the Hexagon processor of the modem handles radio stuff and lots of the layers of LTE.
Good question! I wasn't too concerned about this, because the only way you could even interact with the OS where the server was running was via HTTP requests, which are fairly limited in nature. The OS or kernel itself wasn't directly exposed per se.