This is a really good idea actually. Prefabs are one of the easier things to make in world builder and one of the things that is easier to control and have complete creative control over. Episode 3 shows it off.
I agree with your other points too. People have to realize the devs are trying to make something that can create worlds for us with limited involvement from them. If they lose out on a bunch of dev time merely policing people’s world builder configs and can’t give us wearables, hunters, titans, etc. etc. etc. I think people will be upset.