I personally would like to see a person on Oliver's list that mirrors his father some body that knows he has failed the city and regrets it. Ideally it would be someone Oliver has to get close to but not as Arrow and is afraid of coming forward because of what might happen to their loved ones (I mean come on a list that long has to have a few keeping quite out of fear) then at the end of the episode when the person dies they say the same thing to their loved ones "I'm so sorry I didn't save our city I helped destroy it."
The real reason I want to see a plot like this is that I don't see everyone on the list being a hardened criminal. There have to be a few who are at least a little like his dad. I Also think it's likely that some people were just young fools at the start of their careers with no idea what they were getting into. Also I'd like to see how Oliver would handle such a situation where this person is as guilt as sin while also remorseful but can't come forward or their loved ones pay the price.