Josh - Medical is really his forte and I can't imagine that he'd be more useful elsewhere. I'd sort of considered him as having a definite "on duty" time every day, but also be "on call" in the case of healing-necessary emergencies the rest of the time.
Jimmy - He's totally a jack-of-all-trades with former experience as a sewer rat with the Morlocks. He's quick, small and eager, so whoever needs someone like that, he's your guy.