I'd think most of the civies on Enterprise were scientists of various sorts. Keiko sure fits that role. You'd also have your odd historian, linguist, and the like. They are supposed to be the tip of Starfleet's exploration arm, after all.
I tend to think a Galaxy-class starship is as much a mobile starbase as it is a deep-space exploration vessel. In that capacity, it carries out the additional roles of a Federation embassy and township, IMO.