As you've demonstrated, however, there are two conflicting senses of the word "sustainable". Sustainability for a business means that it accumulates more capital than it expends. Sustainability for human beings is a much fuzzier notion that is tied up in the idea of health: the health of the individual, of our species, and of our environment. We can sacrifice health from these areas to reach different goals, but if our actions continuously deplete it, then they aren't sustainable.
Is it possible to express the human sense of sustainability systematically? I'm not convinced it is, as I think it requires vision and sensitivity to understand health. So I think we need a legal structure which is sensitive in this way in order to create a sustainable society.
Ideally, sure, that sounds great. But it has, thus far, proven to be unworkable. The drive for profit supersedes virtually all else, and much "not good" has been done for that cause. Worse, there has been little to no recompense, even when the public good has been harmed egregiously.
In spite of this, even now, a major ideology says that we need to roll-back what regulations there are.
The political and economic climate don't currently exist to implement what you advocate, but, I do think it's a worthwhile effort. In the meantime, I don't see the downside to encouraging companies to be more socially-oriented, and rewarding those that actually are.
I would prefer a society where we all accept that this is the only thing corporations are capable of being and then structure the legal systems in which they operate to ensure that their actions don't contradict "the greater good". "Psychotic entities whose only goal is profit" will do fine in any environment, despite lamentations to the contrary.
The PR incentives you're talking about only incentivize companies to look like they're doing nice things. Sometimes the easiest way to achieve that goal is to actually do nice things, but not always.