Maybe charging stations could come with N full charging cords and 2N trickle charging cords and it would be socially acceptable to replace someone's full charging cord with a trickle charging cord once the car was full.
The first n cords to be plugged in becomes a primary (read full) charge cord.
Once n primary cords are in use, any subsequent cords start as secondary (read trickle charge -- an aside, do EV's really need to be trickle charged). Again, in order of arrival, the secondary cords are put into a queue.
As the initial batch of n cars reach full charge (or maybe 90%), primary cords swap functionality with the next secondary cord in the queue.
