They could put all the USB C logic required for power negotiation in the molded connector of a USB C cable and expose 5 contacts on the magnetic side of the connector. [gnd-pwr-data-pwr-gnd] that lets you plug it in either way.
You would then have a cable that was USB C PD on one end and MagSafe on the other. You could carry your USB-MagSafe cable and still use any USB C power source, or bring one with if you like.
It isn't a full USB C with it's score of hair thin wires, but it lets you have some beefy power and ground contacts and enough I/O to chat about voltages, currents, and what color an LED might want to be.
You would then have a cable that was USB C PD on one end and MagSafe on the other. You could carry your USB-MagSafe cable and still use any USB C power source, or bring one with if you like.
It isn't a full USB C with it's score of hair thin wires, but it lets you have some beefy power and ground contacts and enough I/O to chat about voltages, currents, and what color an LED might want to be.