I would prefer no idle fee if the station never fills, and a warning when the station is about to fill, and a very fat fee if it actually does fill, including perhaps start with a flat $10, and then add $1/minute or even more. But only if I got a warning and didn't move within 5 minutes. Give some of my fee to the person waiting. (Let me set the warning buffer time, or set it automatically based on the walking distance from my phone to the charger plus a couple of minutes.)
How do they warn me? Track drivers on the way to the charger who have said "navigate to supercharger." They know when they are getting there. If somebody forgets to navigate to supercharger, then they may have to wait without the compensation, though as soon as they plug in my clock starts. (Their car should also notice they are waiting at a supercharger and say, "Click OK to indicate you want to charge, that will alert drivers of the cars here to come move within 5 minutes or pay a fine that you get 1/3rd of.)
I think it's stupid that if a station is at 51% I have to get up from my dinner to move my car. It benefits nobody. Just raise the price for really blocking a station when somebody wants it until people are just as motivated to clear the station, and don't punish anybody if nobody was actually inconvenienced.
It might be different for V2 stations, which is what existed when they made the 51% policy. Maybe the rule there would be that I pay if I'm the reason there's no free pair. Though note that when I am there, the paired stall with mine is a 100% stall if it's open. The arriving driver should be told it's a good choice to take. Tesla knows if you move your car after charging, though at present it doesn't seem to use this -- ie. I think you can unplug and stay EV-Icing the spot without idle fees.