The ideal solution would be to replace the single gang box, with a 4" square
deep box, or simply a 2 gang telecom mud ring. You don't actually need a
box for speaker/telecom/data/coax. You can get rings that can be cut-in
and mounted directly to the sheetrock.

That sounds doable, but one side would require an eight port module and
the other side would require the snap in connectors for coax and
ethernet. I never saw any double gang wall plates like that, so I
would be back to square one?