Except that was only from a "fluff" point of view. If melee combat is enabled, there's nothing to prevent a "Clan" player from using melee attacks, barring it being disabled for the Clans.
Honestly, I'd really rather the Clans not be allowed as a player option, because of the gross imbalance. There isn't a BV (Battle Value) system like there is in tabletop to assist in balancing the forces.
Off the top of my head, the "easiest" way to "balance" a Clan vs IS match is to make it a 12 (IS) vs 5 (Clan) set-up.