First off, I want to second (third?) everything hS said. Very good information, that.
Secondarily, in general I feel like Non-action Departments offer a more "slice of life" experience. Very similar to what you might get in an Action Department interlude. You get to explore the zany happenings of the people who rarely leave HQ, but are just as insane as any assassin or bad-slasher.
Third and lastly, I highly recommend writing a Non-action Department if you want a change of pace from missions. It's a lot of fun.
There's an agent or two for possible future use who I think would fit well in a non action department, but I've never written for that category before, the non-action departments (Well, yes, I did... more