I have noticed several times in a day many users asked questions that have been asked before. There is a list of suggestions as users type in the Title field but it's like most users don't look or overlook or something different.
Like today I wanted to ask "How to re-arrange my favourite tags". I searched and two records came up not related to what I wanted to ask. Then I assumed nobody had asked it. Then when I typed in the Title field, I saw three out of the suggestions that is exactly what I needed. That was because I know the penalty of asking duplicate questions. Most new users overlook this.
My suggestion is this: Is it possible to make the first 5 or 10 suggestions as the first answer with an anonymous user (e.g. community wiki, or another name) or as a comment. This will force the user to see the existing duplicates and also stop users responding with "Possible Duplicate" in the comment.
I think comment will be better. It is easier to delete a question with comments than a question with at least one answer. This will reduce the number of duplicate questions on StackOverflow
If the links don't meet the OP's requirement, he could then indicate so people would answer the question.