Hi, I understand. It's awesome how you're experimenting with the collaborative blogs!

I agree that content management there can be a challenge and it's not even clear how to do it right:
1. You might want to specify included hashtags per author - different for every npub.
2. You might want to "map" some hashtags to others on the site - your proposal above.
3. You might want to be able to edit metadata of each post to "reassign" it's hashtags etc.
4. You might want to just manually add all the posts you need without relying on hashtags for filtering.

The last 2 points seem like the most versatile - you can achieve anything that way. But it's a manual process. 
And automated options usually have limitations  - eventually you'll want even more customized filtering.

I'm happy to explore these options with you to figure out the best way to build collaborative blogs!