Do combination banks need to be considered monopolistic again?

First, a general thought and then back to the question.

I have heard that at one time Henry Ford tried to bypass suppliers by making everything for his cars. From the tires to the seats, Ford thought he could do it as one company and it backfired.

If this be true, can we not now see the weakness of combination banks not as "vertical" monopolies of one price and sector, but of dangers to themselves and us as "horizontal "monopolies across savings and loans, investments, and insurance services. By trying to capitalize on each sector, the banks spelled doom for themselves by trading internal money internally. This internal exchange seems to hide losses more easily and advantage goes to spread of debt.

The disadvantage is that of saturation of debt. It would seem that only so much loss can be spread over a certain area before the debt would be bigger than the area itself.

In Ford's case, if a loss were to be taken on any venture, the whole would absorb it. The point of critical mass would occur when an entity that would normally survive by itself, must carry the spread of debt of others and thus, would not be able to support itself and the "spread". This would compound the spread share to others and surviving entities would have to support it with even weaker ability with each failure.

Ford, as I understand it, now runs all of their businesses as separate entities so as to distinguish spread debt and real debt.