I would be fine with giving skirms some armor as a way of differentiating them from other ranged units. Ranged units don't have the same diversity that melee units have.
However, I strongly disagree with giving units dual attacks en masse. All this will do is make the gameplay confusing. The core units should remain very simple, so I would only be ok with 1 or 2 unique units with dual attack abilities. Ie only legionaries can do the pilum throw, but not pre-reform swordsmen.