I am of the KISS school. Cheap enough and just 'good enough' will sell a higher number than a kitchen-sink device.
Look at the used (ebay) prices for the original Roku M500/1000/2000 devices. Even years after production ended and in the absence of firmware update support these are **still** selling for a high percentage of original MSRP.
Ubicom could do worse than cook up a single-chip implementation/emulation of an M1000 updated with modern networking.
Or, two boxes. The 'base' box is the wall-wart, DLNA, audio, powerline network, web config/control interface, maybe an LED status light or three, etc, etc. The expansion box carries the SPDIF/7.1, wired and wireless network, IR remote/Girder passthrough back to the MC server, interface for a nice fancy informative VFD display (like the Roku M2000), etc.
The base box plugs into the wall. The expansion box connects to the base box via USB or something simple like that. USB 3 might be needed not for the interconnect speed but for the additional current (1 amp) that it can deliver over USB 2.
Another way to do this would be to put a few USB ports on the base box. Then a user could add their own wireless dongle, a sound dongle for SPDIF (like the Turtle Beach products) or a dongle for wired networking.
For design hints look at how Addonics has their disk array products carved out. Lots of config options there.