Mike-WSM...
Lindy knew that with 1927 technology, engine failure = swimming lesson more or less regardless of number of engines. (The Do X was still on the drawing board.)
Other comments...
Small mixed fleets might not be as silly an idea as they once seemed. As aircraft become more reliable and the global supply chain becomes more efficient (how far am I from a FedEx, even if I'm deployed?) then you should be able to operate with a smaller fixed logistics base (no big warehouses or parts repair) or use a commercial-type base plugged into the global market (see Swiss AF/RUAG).
At the same time, the Intertubez, better relationships with potential coalition partners and the more widespread knowledge of a common language permit collaboration with other small operators.