I'm not so sure. This one is actually pretty clear. Like the ruling states: If Congress wants to fix this they can do it with a very simple bill that changes the law. That is not the role of the courts.
The interpretation, too, has been spelled out several times in speeches and interviews by the authors.
They only let subsidies go through state exchanges so voters would push states to develop their state exchanges so voters can get the subsidies.
The wording was on purpose to drive states to absorb the costs of creating and maintaining state level insurance exchanges, because voters would want the subsidies only available that way.
The case against the individual mandate was very clear also, but Roberts rescued it anyway.