Back in the day, when dinosaurs roamed the earth, before USB, 3Com used to make type I PCMCIA (and, later, Cardbus) ethernet cards which used a short 6" or so dongle to bring the proprietary-but-nice latching outward-facing card-edge connector out to a standard modular jack. Variant dongle cables were available for the other 10-base-T physical connector types, but these were really rare. The 3Com cards were available rebadged as Dell, IBM, etc. I don't know if these dongles are still in active production somewhere in China, but they are still semi-available through ebay and such. "3Com dongle pcmcia" are the key search terms.
If we're going to reinvent the wheel, it might be good to reuse the old latching connector and dongle design, if it isn't patent-encumbered.