As you know, this is basically why we made inbox.nostr.wine. I really don’t think it works out of the box with a typical paid relay. 

It combines I think the best two properties of 1&2 in a way that works.

Anyone can write to inbox WITHOUT AUTH as long as the note tags an inbox subscriber. 

Then any inbox subscriber can query for their giftwraps only after AUTH so we never leak that event outside its intended recipients. 

Lastly, we address spam by letting kind 1984 reports from any subscribed user automatically delete any note they are tagged in.