FFBA stacks with everything but military grade armor, also you half its armor value for encumbrance. Keep in mind though that the entire FFBA suit covers even your face so it isn't subtle. However you could buy the full thing and only wear the half body suit. PPP also stacks with everything but military iirc, it has full encumbrance penalties. Both are in Arsenal. You might want to also consider thermodampening, but it isn't cheap.
..in FFBA do u not need to wear additional hood,booties and gloves to to get max armor bonus from it...