Curate, connect, and discover
There's so many characters that I'd love to make an appearance, but for this question I'm going to have to go with Dr. Hannity from The Inside Job.
Her whole thing is that she sees a potential catastrophe that no one else is prepared for, but instead of saving lives, she focuses on manufacturing said catastrophe to make money.
Imagine what she could do if she used her skills for good! She just needs a little more exposure to ethics and caring about other people, which she could totally get during her stint in prison, and then she could reappear as the Harry Wilson of agriculture development.
Who would be the most interesting Leverage villain to have gone away to prison for 10 years and reformed before making a guest appearance in Redemption?