I'm not exactly sure. I mean, the tech for it certainly exists. You can just build a ship with armor, guns, ECM, and whatever kinds of shields I implement. But once you get to a crew of more than four, the game is optimized for blended-role ships that balance multiple missions at the same time. Restricting yourself solely to a combat role might be pretty boring.
Viewing post in The Galactic Line
Ya of course, Having a ship that just does the Pew Pew going on a humanitarian mission for some planetary disaster is not going to do much to help the people in need. You could still fix the issue by just blasting the planet away along with the whiny needy residents ;).
Say that a governing body needs a escort for one of their not so pew pew ships. The section of space they are traveling through is a lawless place, known to have some nasty pirates. If they use one of their warships it might Upset their neighbors, since this nation has a habit of being more on the Hawkish side of things.