I would like to see a clear division of damage types added to Heroes of Might and Magic 6, like in King's Bounty. Yes, yes, I'm against total copying, but the system there is really good.
In King's Bounty, there are five types of damage - physical, magical, fire, poison, and astral - and four types of defense. There is no defense against astral damage. Each creature has a damage type and bonuses/penalties to defense against the four main types. Spells and War Spirits/Dragonling also have damage types.
And also add a penalty for ranged attacks for each cell.