my two cents here (sorry I am late) but I chose to do the "roadblock captain". No they do not have a backpack. In order for me to go SWAT though, I would have to level up to PO, which would require me to build a pack. Which I dont see as necessary because the armor doesn't have it. BUT - I have accepted that as a necessary standard that should be met. If I really wanted to go SWAT, then I would build a pack to make PO.
IMO - the iconic Sandtrooper is identifiable by their pauldron. No pauldron is just a regular TK that's dirty.