I could do a stream just about that! I am currently writing a peer reviewed book on Blueprints with a few of the Unreal Engine Community experts. So we’re going to talk a lot about use of Macros, Functions, and Events/Delegates in the book. BUT, I can definitely talk to Epic about doing another stream on that topic. 
You bring up a lot of excellent points. These are all extensions of this conversations. It’s not something that I could just explain in one breath, of else it would be common practice.
What I hope is by introducing a wave of different topics which I think are foundational to understanding where to place logic.
Think of this way, if you take the time to effectively break your code into pieces. It’s much easier to identify where it can be improved, but also just as easy to understand where to interject subroutines to expose parts of the functionality in graceful way. Instead of constantly making hacks when you need a particular variable.
The problem is if you don’t try to organize your code with any sort of patterns or principles, it’s nearly impossible to effectively improve your code. Bugs are harder to see, repetition is harder to see, and when you come back in 2-6 months. Can you remember what you where doing?
So all very good points, I’ll continue to bring up over the streams.