I have two of these devices and they seem to be pretty kickass as far as hardware specs. The firmware on them is a different story!
I pulled the board out of this one to check it out, but that's about as far as I have had time to get. I'm not sure what the deal would be with the modem side of things either... I'm guessing that could be a problem?
Here's some info about the hardware: http://en.techinfodepot.shoutwiki.com/wiki/Arris_NVG448B
Here are some hw specs:
With the BCM63148 i think it should be possible to add at least partly support, but this has to be done by anyone that owns such a device.
Here is the target specific code for this device:
BCM63148 (SOC): probably yes
xDSL modem: never
BCM43217 (2.4 GHz): never
BCM43602 (5 GHz): maybe, brcmfmac
…not a whole lot kicking left.
 only basic support via b43, limited to 54 MBit/s
That sucks... without either wifi or xDSL working I guess its not really worth doing. I do remember reading something about the proprietary driver issue with broadcom DSL stuff.