#1 is obviously the best. Okay that might be an overstatement, but really, all the alternatives pale in comparison. They either are browser only, require existing clearnet presence (DNS, PKI), or have real logistics/management hurdles (Zokoo's triangle).
We already have naming systems that are secure, human readable, and globally unique. Why would we bother with the registration politics nightmare of a remote authoritative naming repository? Or many nonauthoritative ones that can have global naming collisions.
NameCoin/GNS/BlockStack might even mainline the client code to make it compatible with Tor. And if not, a small shim would be super simple (disclaimer: I have not read the spec yet). Doesn't NameCoin already have a a record type reserved for .onion addresses?
The answer has been right in front of our faces for at least 5 years now (NameCoin, maybe even others before that). I honestly can't believe it has taken this long to get to where we are, and we're still in the proposal stage. But I'm glad we're getting there! This is a huge step for onion services!
More information about formatting options
Drupal Design and Maintenance by New Eon Media
Drupal Development by Chapter Three