I think the protocol on which PDUs are exchanged on is a bit orthogonal to the PDU protocol itself here, but the split-mode networking protocols (FTP, IRC DCC, mosh, SIP, etc) always do end up getting less used because establishing two different connections is a bigger burden and there really needs to be a great advantage to doing so, and often require other considerations (better connection tracking, TURN/ICE servers, etc).
For a localhost/UNIX domain protocol, it might work since most of these considerations are significantly reduced.
As to DSCP, it might be useful across controlled networks but in general, in my experience it's not really ever honored broadly.
Back on the original topic, when I was building this for my Linux distribution I ended up just using basic JSON with TLS (for client certificate authentication) though since having authentication for remote management was a goal, and once I was already having to perform a TLS negotiation then the PDU consideration for performance wasn't something to really spend too much time on.
For a localhost/UNIX domain protocol, it might work since most of these considerations are significantly reduced.
As to DSCP, it might be useful across controlled networks but in general, in my experience it's not really ever honored broadly.
Back on the original topic, when I was building this for my Linux distribution I ended up just using basic JSON with TLS (for client certificate authentication) though since having authentication for remote management was a goal, and once I was already having to perform a TLS negotiation then the PDU consideration for performance wasn't something to really spend too much time on.