I understand your concerns with moderation, but I don't see how what I am proposing would make things more difficult?
What would stop a troll to create different accounts on all the other different instances, or create another account whenever they get banned?
I am not sure what "instance members" you are referring to, here.
The topic-based instances are closed for registration, so there are no users there.
If you are referring to the communick.news instance: it is only configured to have admins creating communities on it and the general instructions are to use https://fediverser.network as the place to discover communities.