I'm not saying any of that is easy to model - far from it - but I'd be surprised if someone simulating those complex systems never resorted to "black box" thinking. What that means is that you're not interested in the real-world logic and/or electronics level of the box per se; instead, what you need to know exactly is its behaviour, i.e. the inputs and outputs it provides and its connections to (and dependencies on) the whole, and then work out the innards from there.
Again, not saying this is easy, because it isn't. But at least it gives you some freedom in how to implement the box, instead of trying to clone it exactly.
Anyway, I do agree that modelling a WW2 A/C is most likely easier than modelling a 4th generation fighter jet, due to the complexity of the systems the latter carries.