This is a great idea. But calculating it based on your criteria won't be trivial:

> is the first follow of a new account

This can't be calculated with certainty, because clients can rearrange contacts, but most of them don't, so might be ok.

>  follows the new account within 24 hours

Not possible unless we track the full history of contact list editing by the advocates. We don't. 

> is author or recipient of first Note or DM with the new account

OK

> “engages” with new account “regularly” during a period

A bit complex but ok.

> is “trusted” by trust.nostr.band

OK.

If we replace the second condition with just 'Follows the new account' then it might work. But I can't promise to deliver this soon - quite complex endeavor with an obvious result. Do you really need the confirmation in numbers to keep building your onboarding tool?