As you mentioned,
I recently learned that physics-based Static Meshes that are children of Scene objects will detach as soon as the game starts.
The detaching happens when a component begins to simulate physics. The hierarchy of what is a parent and what is child is still maintained though, which is still useful. So my suggestion, when the child simulates you will probably want to make a new physics constraint component to attach the child body to the parent body.
Hope that helps you with your system rework 