Would you prefer an approach like this https://data.nostr.band - common kind for all query type, d-tag to specify query params. Or a separate kind dedicated to each of trending X, curated Y?
Discussion
Ndapp is an interesting approach.
I think a common replaceable event kind published every 15-60 minutes (or daily) could be useful to client apps for trending. People can select from different pubkeys - for which seems better quality, etc. You lose historic, but likely ok.
Skews for people, topics, hashtags, relays, etc.
The main issue is scope, or abuse. Faking results to benefit them, or maybe not dynamic enough. And automated content that’s repetitive, by count, ranks highly today without filtering.
Gotta think about this now, didn't consider this approach you've outlined, it's compelling too