Yes, this would lead to an enormous productivity boost for composing blueprints. Ideally it should be possible to add them directly as components (like a point light, for example) so you don’t have to ‘extract’ the actual child blueprint from the child actor at runtime first, cast it and then creating an additional reference to it.
You should be able to convert actors from the scene into components:
Secondly, you should be able to add your actor blueprints (along with their own components etc.) as normal components in other blueprints and preconfigure them.