I personally think a triple Ram Rider summon for Dain would be enough similar to summoning Warg Archers, would be a nice variation on Iron Hills King Dain's Level 8 power. Because, I am probably wrong, but Dain Ironfoot's ability was also a summon correct? Like, summoning multiple dwarven realm warriors. Or the Assembly Hall? Anyway, I'd vouch for that. Ram Riders are pretty unique units and it would seem like a waste of good material to not implement them somewhere, to me. It would also make them more exclusive, without changing the major weakness of Dwarves that much: Lack of cavalry.
Battlewagons..ehh, they are a little lackluster, I find. As a supporting unit they have some fantastic upgrades, but they die extremely fast. Perhaps the unit could use some tweaking as well?