GM should add more 12 VDC ports in every EV. In addition to one for the rear seat riders, they should add one in the trunk area for the air pump if you need to add air to the rear tires. My 1995 Buick Regal had two, one near the front passenger's left foot (under a small spring loaded cover) and one in the center console. My 2009 Chevy Equinox only has the one in the center console but I added one in the rear area (where the jack is stowed) and it is powered by the tail light (it has its own 10 A fuse).
So I recommend all vehicles, EV or not, to add one in the trunk area for that day (or night) when you need the air pump, and don't want to pass the long 12 VDC plug and cable through the driver's side.
Ford hybrids have one better. Since the first Escape and Fusion hybrids came out, they have a 120 VAC outlet. The Fusion has it in the rear of the center console in addition to the two USB and the single 12VDC outlets. I haven't verified, but the Focus Electric and the C-Max hybrid should have the same.