OK, looking at the Marshal from Far Horizons, I was trying to decide what would make a good second specialization. Mercenary Soldier looked good for the Field Commander aspect, but the flavor was a little off. I kept looking and found the Peacekeeper in the Force and Destiny Beta.
It adds a great set of Career Skills for a cop-type character (Discipline, Perception, and Piloting [Planetary]) and it's easy to get some great stuff off of the talent tree without being Force Sensitive. At worst, you might waste 15 XP on Enhanced Leader (useless to you until you get Force Rating 1), but you can go around it if you take the long route. In addition to the leadership-based talents, it adds a lot of Toughened.
If you decide at some point to grab up FSEm/FSEx for Force Rating 1, you've already got the groundwork in for getting that Force Rating increased through Peacekeeper. If you decide not to go Force Sensitive, you've still got a great cop!