Where are all the missing links?

Spoken like someone who doesn't design machines for a living. As someone who is well-placed (for once) to comment, machine design is an exercise in untilising a multitude of previously existing element in order to arrive at a completely new device.

What is the best way to form a fuselage to withstand pressure differences between outside in inside walls - irrespective of how the pressure difference arises ? A cylinder. What your talking about is details. A cylinder is a common design for such vessels for one reason - intelligence has figured that out to be the best design