I disagree with Krensky here, and think it's fine. His own argument goes against him - by using it with Padded + Fittings or a Harness, the existing ability is actually better (these soldiers will have +5 Defence and some DR and Resistances, rather then just the Defence bonus, since these Armours have no defence penalty). At worst case, it changes the Soldiers Defence column from Medium to High, with a limitation (a not small one either: mid-level soldiers can easily achieve over 10 DR, making them effectively immune to many weapons - this guy is 2 points harder to hit, and immune to nothing).
I say go for it. It's pretty edge case, but I like it. I could also see the Assassin's ability working for the Soldier, so go with how you feel.