[detaro]

USB with it's max 5 m cable length unless you use special repeaters etc wouldn't be a good choice IMHO.

If you wanted to switch to something common, I'd personally say Ethernet (or something "normal", and a specified transport over Ethernet). Handles the distances and data rates more than fine, parts to implement it are widely available, it's already used more and more in stage and recording setups, so specialized components are available too. In the audio sector, standards to distribute precise clocks are around, one could maybe reuse those to get it past P2P connections (although that kind of gear is still kind of expensive right now). Still quite a step up in complexity though...

[ATsch]

There's already a lot of professional sound gear that uses Ethernet with a custom layer 3 (iirc) protocol for digital audio, so supporting Ethernet would sure make sense.