So having played a number of games with each of the Dwarven factions I had an idea for a small change that could be applied to Lake Town and Dale that would give them a bit more defense while also giving Bard and Brand a small buff in the long run that's not all that overwhelming.
The idea I'm proposing is that when the Watchtower is built either Brand (for Dale) or Bard (for Lake Town) could garrison the Watchtower similar to how Saruman can enter Isengard's Citadel. Inside of the tower both of them would attack enemies that enter the area (giving the Tower a second shot for a slight defense elevation) while perhaps granting an aspect of their leaderships to the area around them (of course this would still be applied just to the units of Dale / Lake town and would be in smaller amounts to their normal values as it would be an aura effect that would not take their level into account).
The other concept in this would be to, again, similar to Saruman, allow them to fire the Black Arrow at an individual unit from inside the tower, utilizing it's mounted weapon. The idea being that this arrow deals less damage than Bard's usual one, but maintains it's trait of being stronger vs monsters and with a cooldown similar to that of Ered Mithrin's catapult, allowing them to better defend the town from monsters.
I do understand that in reality, there's no reason that Lake Town / Dale require this kind of change, I just think it would be a nice addition to them that would also allow them a bit more utility similar to that of Ered Mithrin while giving more worth to having the men of Dale / Lake Town rally to it's defense.