If I understand you correctly that is exactly what I want too.
NIP-29 is already that beacon of relay-powered centralization in amidst a Nostr decentralized ecosystem. If you haven't read or understood NIP-29 I forgive you, because the NIP text itself doesn't explain much. If you can come up with a more pronounceable name for the concept I would like to make a website explaining it. Please help.
The idea is that each of NIP-29 groups can have chat, forum threads, live voice/video or whatever else (or just one of each), with moderation enforced by the relay on behalf of the group owner.
If you read the discussion I referenced above it is me and
@Anjhc trying to come up with a system for having a parent group and multiple children groups, which would be like a Discord server. So you could either have a single group with everything in it, like Telegram (which I prefer), or a bunch of sub-groups, like Discord. Please send valuable input if you have.
You also describe an easy to set-up relay for communities. I don't know if you have seen
https://github.com/fiatjaf/pyramid, but that's what I'm trying to do there (the setup specifically is the part I'm most proud of, because it is as simple as it gets and it doesn't use Docker). There is a lot to do there and I'm taking suggestions from anyone. Please send yours if you like it, or join our NIP-29 room (link in the README).