Imagine if Epic had just one employee whose sole job was to do nothing but crank out little mini-prototypes like these day after day. Within in a year or so there would be a vast library of little components covering just about every imaginable gameplay situation. Having a huge library like that available would add incredible value to the engine and be something no other competitor offers. They wouldn’t even need to have finished artwork really. Just simple placeholder graphics like the templates in the launcher would do.
Whatever community efforts come along eventually, it would be highly desirable to also have something like this from a professional at Epic so that best practices would be followed and adequate testing done.