to "cap*" your scout from auto AA you need something like 3.000.000 real hab.
to achieve that at lvl 120 you need a +12 BVE (109 vets full experts) if you want to cap with lower base (11 or 10) you need to add more vets in order to reach 3m.
* i mean cap by being imune to some nations (like IJN or KM) auto AA and while still not imune get good resistance against best nation's auto AA (US)