I'm surprised that nobody has mentioned Jesus Manzano or Filippo Simeoni. They are about the only two ex-dopers who I'd trust if they chose to remain in the sport. Even then, I'd be sceptical of Simeoni. If Kimmage chose to get back into cycling in some capacity I would include him as well.
If true, some of the things I've heard about Zabriskie would go a long way to restoring some credibility but I wouldn't hold my breath.
Hamilton, Rasmussen and Landis have given some great insight to techniques etc but I still don't think they should be welcomed back in to the fold, unless it involves suggesting improvements to anti doping.
Barry, Hincapie, JV, Zabel, Riis, Stephens, Julich, White etc should have no place in the sport. Disgusting hypocrites.