A spring loaded reel with a charge cord rolled on to it that can be mounted on the ceiling. The charge cord can be pulled down and locks in place then when pulled down slightly it will retract much like a window shade. The entire assembly already exists from a third party minus the Tesla charge tip/hardware.
Would be nice to have two different models. Less expensive one for a 10KW single charger Model S & a 20KW high power ceiling charge model, HPCC.
A different approach would have a short 1 ft version of the current mobile charger cable that could plug into an existing cord-reel.
Cost from third party 50 A retractable reel without the charge tip/hardware is between $500 and $700 (depending on if they are running a sale).