Um, no. Because the RATE of charge delivered is highly variable, depending on the Supercharger and whether there's a vehicle charging in a paired stall. A per-minute cost while Supercharging thus punishes many who would now be paying for something (e.g., the full 105kW maximum rate) that they may or may not get. And yes, I know about tapering, but that's a different matter not related to maximum charge rates.
Any policy Tesla implements is going to have problems.
If Tesla encourages drivers to charge only what they need and then leave - that should reduce the time where a car connected to the 2nd charging station would be getting the slower charging rate.
Under a simpler per-minute fee plan, you'd also have the option to wait to connect until the other car is finished using the charger - and then get the fastest charging rate, at the lowest cost.
Of course, that creates a situation where people could pull up to a charging spot - sit there - and only connect when the other car disconnects, effectively blocking that spot for use by anyone else.
For any policy Tesla creates, it will be easy to come up with cases where people could subvert the policy (such as the above suggestion of setting the charging limit low, and then moving it slowly upward every few minutes to avoid paying the idle parking fee).
That's why I'd recommend keeping the policy as simple as possible - and Tesla can then focus on closing whatever loopholes they create with the policy - such as implementing a better way to monitor charging station availability than which chargers are currently connected to a car (video monitoring of the SC stalls?).