In more urbanized areas like Orange County, most if not all of the Superchargers should probably stop at 80%, at least whenever they're busy enough for idle fees to be applicable. That could help to reduce congestion immediately, without preventing anyone from driving anywhere.
Rural Superchargers are another matter. At Inyokern and other rural SCs, when the site is busy, I'd have no problem with everyone being forced to stop Supercharging at 90% if destination chargers were available for topping off. I'm suggesting a threshold of 90%, rather than 80%, because most cars won't get more than 9 - 12 kW out of a destination charger. Even for a car at 80%, that's much slower than Supercharging. Another benefit of adding destination chargers is that they would be better for people staying in adjacent hotels, as there are many Superchargers that are close to overnight accommodations.