Those are interested ideas. But it begs the question: How to enforce compliance without regulation?
For example, corporations are strictly creatures of law; they exist IF and Only If, and in the form that the law allows, at the pleasure of the government.
So, rewrite the enabling laws to state specifically and explicitly that corporations have affirmative responsibilities not only to the shareholders, but also to their workers, the community, the nation, and the environment, etc.
That alone immediately gives cover to any executive or board taking action that benefits those entities and perhaps not so much the shareholders. So they have a defense against shareholder suits that seek to force action or compensation away from corporate responsibility. Plus, there would also be a cause of action from the other parties for failure to take care of their interests. Obviously, this could go too far in either direction, so it must be carefully written, but this is the general idea.
There are many other ways, but that's the idea, don't rely solely on regulation.
I fully understand that that will not happen by itself.
What I'm advocating is changing the STRUCTURE in which they operate so that "becoming nicer" is prompted by the system. The current system fully expects only the primary goal of maximizing profit/value for the shareholders/owners, and minimal compliance with anything else.
This is despite the fact that EVERY corporation enjoys massive benefits of operating in a country that provides everything from transportation infrastructure, a reliable legal system, an educated workforce, to military protection of global shipping lanes.
It would help to embedding into the law the concept of corporate responsibility, by providing a cause of action for irresponsible corporate actions. Expecting the corporation to take care of the workers, and the environment. E.g., In Germany, it is required that workers have seats on the boards and workers have much greater rights.
The point is that the law is now, as you say, just [corps are expected to take care of only their shareholders] and [corps are subject to some regulation].
This system has been tried for nearly 250 years, and is obviously lacking.
I don't think iron-fisted regulation will provide a solution. That's already been tried, everyone got annoyed at the overhead, and it was backed off (see Reagan administration), and the corp destruction has ramped up ever since. It literally just becomes a higher priority to corps to do regulatory capture then.
We need to make the system harder to capture, spin a wider web. And that can be done by broadening the social and legal compact with corporations ('tho they'll fight like hell against it).