I had thought about this, but I am not sure how to handle paid RSVP. Monetization matters. We can consider attaching external link, but, I think it is not complete solution
These are ideal and fit into my mental model.
https://event-us.kr/ (korean), https://connpass.com/ (japanese)
But I don't know how to complete implement paid RSVP for fediverse. That's bottleneck