Which cache adapter are you using? I just spent a bunch of time yesterday getting the dexie cache adapter ready for release (coming soon) and was thinking along the same lines for a caching video soon.
Discussion
I use a custom one backed by indexeddb and using dexie too, will port to dexie adapter when is released
https://github.com/nostr-dev-kit/ndk-cache-dexie
Definitely have a look at the code there before using it, I'm not sure all query variations are covered yet.
The code is very old and bad so it probably needs a major reactor but mostly works 😅😅😅😅