Of course, this goes aganst the current grain of financial markets, which want companies to specialize as much as possible (i.e. have as narrow remits as possible that they pursue as ferociously as possible) so that they, the financial players, can decide to build the kind of diversification that they want (or that they can sell back at high price to those companies that have given up stability for the pursuit of specialised profit).

In effect, you are calling for the renewal of the concept of conglomerates, which have better resilience and stability and better encompass externalities.

Or did i get your point wrong?

In the long run, we're all dead. John Maynard Keynes