<3
The more I think on Shane, I think he should be a Goon. His whole thing is that though he works at Joja, he doesn't like being there; he just needs cash and that's the only job in town. So making him a Goon would be a way of saying that he's not really on their side/helping that team win.
I can see Sam as a Tracker, maybe. He's there at the market, doing his business, helping people out, and he can't help but listen to the customers talking with each other:
- I'll buy this to make a nice dinner for us
- Oh! I forgot to tell you, but after dinner I'm going to X's house/the saloon and hang out for a while
And like that he learns where people are going :P Don't think there's any character that would fit into a "Cop" role, but with a Tracker the scummies could find PRs.