How do I integrate complex, coordinated building systems?

You can integrate systems, and where you still trip is the complex jobs where many systems must be coordinated at once, each depending on the others. That is not a weakness in your skill. It is the frontier of it. Coordination at that scale is genuinely hard, because a choice in one place forces choices in three others. The way forward is to stop holding the whole thing in your head at once and start making the dependencies explicit. Map which system needs what from which, and in what order decisions have to happen. Most integration failures are not technical. They are a missed handoff, a decision made too late, a system finalized before another that shaped it. Sequence is half the battle. On your next complex project, before designing anything, write the order in which decisions must be made and what each one depends on. Let that map guide the work. Coordination stops feeling like juggling when you can see the connections on paper instead of carrying them all in your mind. The complexity does not shrink, but it stops being chaos.