I mean there's nothing saying you can't have a break-away cable even now. Look at the Xbox, the controllers are USB and they break near the system if the cable is tripped on. It's perfectly possible to have USB type C and MagSafe at the same time.
In fact, you could probably have a USB-C-to-MagSafe-to-USB-C adapter. Knock your laptop and the cable comes loose, with the adapter left plugged into the port.