A friend may accidentally acquire a quantity of these here spiffy
Affordable No Parking signs , drill them, and toss them along with the requisite nuts and bolts and some Loctite into the frunk. Maybe a tie-dye blue TJ mark on the back of each just for grins. Wish the friend had thought of it ~300 supercharger sites ago.
A few of these signs affixed directly below the Tesla signs, along with the property management company adding some green paint for the curb (both sides) would contribute toward deterrence. Deterrence would appear to be the best option here, given the givens.
Although it seems the security guard's "tickets" at this Thousand Oaks location may help as well. Most people don't know that they can't be towed without signage - and in fact, tow companies don't always refuse. A buck is a buck.
Fact is, though, I rarely see ICEing by ICEs anymore. Couple places come to mind, but ICEing by our own and livery remain the #1 & #2 concerns. ICEing by ICEs is 4th, and it's not close. Only 3% of the network is "busy" anyway. Top 1%-ish being in California, according to those nifty flat panel real-time readouts. As an aside, China has been supplanted by Norway and the Netherlands in those displays (8 are typically California, 1 Norway, and 1 Netherlands - whereas a few months ago, China had a spot or two in the Top 10).