but the argument against that is the fact that you specifically cant wear the vitals kit with anything covering the chest slot (armor vest/jacket full body armor etc) and the arms and legs kits, they cant be combined with FBA.
so you can wear the arms/legs kit with a armor vest and a FBA helmet, but you cant wear FBA with any of them.
actually re-reading and looking at things i think i'm going to change my answer, id say its a one and done basis on the thinking that it is a "set" of armor as novocrane is stating, just like the riot control armor is a set. and when you buy both the riot control armor and helmet you dont double up on the penaltys/bonuses that those types of gear give you.
however i think that if your stacking mutiple sets of items that have limit modifers like this they do stack EX: Armor Jacket, PPE legs/arms, Swat Helmet. you would have the following social penalties: Decrease Social Limit by 1, Gear Access, Increase Social Limit by 2 for Intimidation Tests (3 when wireless) and reduce it by 1 for all other Social Tests with the general public,
so you would be at an increase of 2 for intimidation tests, and a -2 for all other social tests (argument could be made that with security forces you would only be at a -1 because of the wording of the Swat Helmet)