Blue
Ravenous Bugblatter Beast of Traal
The armor and shield bits of versatile feel too fiddly for the final result if +1 against some opponents. While flavorful, I think would be more 5e-ish to just wrap it all up as a plain, always on +1 bonus.
I know that lessens the feel you were going for, with maces and picks better able to breach armor.
I agree it's too fiddly, but also think it's too irrelevant.
Only a fraction of humanoids will be wearing heavy armor or wearing shields. In a urban campaign that would be a reasonable ability. But humanoid are only a small percentage of foe types. Most foes have natural armor and weapons, making the ability useless against well over 95% of foes.
Unless you want to extend it out. Say, Natural Armor +5 or higher counts as heavy armor - this way it makes sense that a dragon's scales are plate are both better attacked by a weapon with that bonus. Not sure what the equivalent of shields is though.