A lot of people probably do program the Supercharger as a nav destination, though. That's where the warning would be helpful, and perhaps with a different color pin to indicate a fault. Things to add to the wish list, I suppose.
This is an opportunity, one that from Tesla's corporate culture I'm pretty sure they will eventually get around to filling by software update, though I haven't read anything suggesting it is in work.
What they should have, and I think eventually will, is a MNav system that incorporates the EVPlanner energy required information, real time status of Superchargers, and current weather - so that given a driving speed (possibly pulled from the road speed limit and your chosen speed assist offset?) It can tell you how much energy you need at each supercharger and plan and guide to supercharger stops. With that info, when you plug in it could give your a time to finish your required charge for the next leg, too (and automatically set the end of charge limit, if desired, though I'm not sure that's useful.)
Taking it a step further, they could have an internal 'reservations' page at the Supercharger station - the strains would still be first come first serve of course, but this list would tell all the car's doing planning how many cars are expected to be there when they might arrive, and in areas where there are several options might allow leveling the load and minimizing the delay by choosing less loaded stations.
Tesla has all the information to do this, and the processing power required on the car side isn't that large - almost all the heavy lifting would be done server side anyway.
I can't imagine that Tesla lacks the vision to do this, so I'm expecting that it will show up eventually, probably in a few years.
Walter