(Thought experiment) I think its easier to frame what that legal structure should be if we agree on what Profit actually means. If I define profit as: Provide goods and / or services people want in a sustainable fashion -- does that impact the story? E.g. if its not profitable (generally), is it sustainable? (I think no). But the converse is clearly not true as profits can be sought at the expense of something less obvious (say, environment).
Profit is the accumulation of capital. What you've described is a way of pursuing profit. Outside of economics, I think the word "profit" is meaningless.
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.
