Simple plugin to give/remove it: https://github.com/Bara/TroubleinTer...removeHeavy.sp
m_bHasHeavyArmor - For Overlay, Speed and (maybe - I'm not sure) Weapon Restriction
m_bWearingSuit - For Armor icon and (maybe - I'm not sure) Weapon Restriction
m_ArmorValue - To reset armor back to 0
And if you want to reset client model, use GetClientModel before you give item_heavyassaultsuit.
(Primary) Weapons that works with heavy assault suit: p90, m249, negev, nova, xm1014, sawedoff, mag7, mac10, mp9, mp7, ump45 and bizon
All secondary weapons works fine.
Thanks to IAmCow
for the tip with m_bHasHeavyArmor.