A more specific role management system that lets the administrator define moderators and assign them to a specific thread. Also, I want to decorate these moderators (i.e. adding somthing to their name, or add a icon, etc).
Topic-specific permissions? That's going to be difficult... and definitely in plugin territory. I doubt many people will want that kind of functionality in core.
You can use groups to define moderators and actually assign a label to them. but being able to define system wide administrative permissions through the group settings would be a huge plus.
I would also like to have different permissions by rank or group. And if we could assign users to those groups based on reputation, that would be awesome.
NodeBB should try to replicate vBulletins role management, there is lots amount of controls and options. NodeBB is lacking in that aspect.
I agree with @julian, I don't think it's a good fit for core.
I think only very large boards would need this feature, and most NodeBB sites I've seen are small to medium size communities.
It would be a great plugin though