I don't get it. Your proposed addon doesn't prevent ninjas, and worse, it can incorrectly label people as such.
You're better off with a "Notepad" like addon where you can put notes on everyone you meet such as whether they are a nice person, that guy is a great enchanter, this person is a average healer, that person is a ninja, etc. And there is already lots of such addons available.
You're not getting the point we're trying to tell you. The addon you want is completely useless and doesn't do anything useful when a much simpler solution is available.