Poly note "CV" is the Next Big Thing needed after MIDI-Out and inbuilt Rex. (Although personally I'd have ranked poly cv ahead of those...
). With those two cornerstones of the FSF done, there is really no excuse not to find a method of enabled this in R8, especially as, and I think this is fairly common knowledge amongst PUF regulars, all existing RE devices have space set aside for future use (in practice the "reserved space" is only really relevant for 1-3U devices, larger devices tend to automatically have some free space somewhere. I'm sure even RP find a slot in between logos).
Really all poly cv means is the ability to use devices to send/receive—at the very least—per voice note, gate on and gate off events through a manually set device-to-device connection, instead of the inbuilt sequencer-to-device connection. We call it poly cv more for convenience than technical accuracy
: "Poly CV" makes it sound grander than it likely is. Whether other parameters, pitch-bend etc, could also be handled via RE to RE systems is harder to judge due to sandboxing requirements and virtual, but quite real, bandwidth limitations.
So I vote MIDI-In/Out/Thru for the Reserved Space!
Dogboy, sir! You've got history of making things happen! Go start the official MIDI-In/Out/Thru thread!!