sign a self-signed tls certificate with your Onion Service's hs_ed25519_secret_key and Tor Browser trusting the tls certificate based on this signature
- In unlikely case tor crypto fails or breaks, e2e TLS is good there. - An admin might terminate onions on one box, and forward the plaintext off to other places, e2e TLS is good there. - Onionland does have some PKI, CA, pinning, and tor signing infrastructures. - Admins might want to play, learn, and do it just because they can.
The browser either has options to import and trust an onion sig over a cert, or you need to add it, or skip it and use today's typical cert methods.
The concepts apply to both v2 and v3 onions.
Would this approach work?
Manually for you, and by users, loading and configuring things, yes. Automagically, browser would need to fetch pubkeys from controller hsdir consensus, observatories, or other methods.
Would it be worth the effort?
For whatever ca / pki structures are already good for, or not. And might help against the rewriting onion proxies...