I should point out you only need 2 wires to each headphone jack, just short tip and ring terminals at the jack.
Before you go too far, something to think about. What if you had a case with a 2-piece top and bottom, picture a clamshell style package. What if these were extrusions that composed 4 sides, and accepted flat panels for the other 2? (Similar configuration molded plastic cases are available, maybe even the preferred choice.) I had always pictured the flat panels as front-back, but you could make them side-side. Now there is a possibility for assembly even with all connectors and controls mounted on the PCB. Yes, the case needs 4 holes for the switches and pots, not too hard to do well if a printed template is attached for drill alignment. Yes, the RJ-45 mounts from the inside rather than outside, but that's doable. Maybe the side panels could be made as PCBs, screen printed even. This concept eliminates a lot of manual wiring of the headphone jacks, no RJ-45 pigtails and doubling the RJ-45 connector count, and it still keeps the connector orientation and minimized depth you have now. Choices, choices....
Before you go too far, something to think about. What if you had a case with a 2-piece top and bottom, picture a clamshell style package. What if these were extrusions that composed 4 sides, and accepted flat panels for the other 2? (Similar configuration molded plastic cases are available, maybe even the preferred choice.) I had always pictured the flat panels as front-back, but you could make them side-side. Now there is a possibility for assembly even with all connectors and controls mounted on the PCB. Yes, the case needs 4 holes for the switches and pots, not too hard to do well if a printed template is attached for drill alignment. Yes, the RJ-45 mounts from the inside rather than outside, but that's doable. Maybe the side panels could be made as PCBs, screen printed even. This concept eliminates a lot of manual wiring of the headphone jacks, no RJ-45 pigtails and doubling the RJ-45 connector count, and it still keeps the connector orientation and minimized depth you have now. Choices, choices....