I spent some of this week making an I/O system for level scripting in Unreal. I have long had thoughts on why these kick ass. Here's an unusually long blog post on:

-why these kick ass
-why they are necessary
-how mine works
-etc etc

https://www.joewintergreen.com/i-o-systems-for-level-scripting/

@joewintergreen Great read, thanks! I also once made a systaem like this, but it was much more like the Black Mesa example you showed. That did grow out of control quite fast, but the idea is awesome.