I don't see a problem with having the same set of agents running 3 different campaigns - each one is associated with a skill group, and the agents are members of the 3 skill groups.
What I do have a problem with is an agent mixing a preview and a predictive campaign. I have never saddled an agent with such a task, but it doesn't sound good to me. I strongly suggest splitting off the preview guys.
Regards,
Geoff