I'll only speak to the armor question; I'll let the better gun build players weigh in on the build. Shotguns benefit *hugely* from proper field placement, so you're really going to want mobility. Even with the 30MP from Sprint, you're going to want more movement points pretty frequently. I'd avoid going full tin can if you really intend to be shotgun only. OTOH, if you can find it in you to drop one of those feats and slip in Armor Sloping, you can build a very low armor penalty Super Steel suit, though for that you'd have to pull a few points from Hacking, Persuasion, and a bunch from Throwing (why so many, btw?) and drop them into Tailoring.