If charging away from home is important, and superchargers are not sufficient, you'll get more bang for your buck with the CHAdeMO adapter than the dual chargers.
I don't know about that. Tesla is giving away HPWC's to businesses that install them, and that has really been taken advantage of a lot lately. I just noticed a couple installed near me, and the Supercharger map is now showing them with a smaller red circle and lightening bolt. If you travel with the car and have dual chargers, these seem to be more available than CHAdeMO's and they are likely to increase at a faster rate than CHAdeMO's:
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You do need to make sure you can use them, since many require that you are a guest of the business before you can use them.