>>96159438
Unless there are erratas I don't know about:
-Mercenaries don't have access to slings.
-Swordmen's reroll to hit when charging only applies to attacks with a regular sword so you are paying 10 points extra for a skill you aren't using.
-Armour isn't really worth the cost of two more warriors plus weapons. That said if you want them to have armour for theme/model reasons go for it.