JohnnyCanuck
Headphoneus Supremus
Why not just use the RJ-45? Adapters are cheap and serial AICs are cheap too if you don't have a legacy system laying around.
What I am suggesting would involve the end user downloading an update from Schiit via the internet, copying the file to a USB thumb drive and then inserting the thumb drive into the device in question for installation. This method is in use by several other manufacturers at the moment and should be relatively easy to implement.
JC