I was thinking along these lines the other day. With the coming of the Kharadron, it seems as though the GW design studio has been taking one aspect of a race that previously existed, then blowing it up to a Battletome sized force. It'll be interesting to see which features they seek to explore.
When It comes to the Duardin, we have Fireslayers and Kharadron, representing fire and air respectively and taking previous design elements of the stunties and turning them up to 11. With the Slayers and the Gyro's having been expanded upon, I think it might be fun to take the Miners and really explore that aspect of the Duardin. They could encapsulate everything 'Earth'. Lumbering stone golems, burrowing mole-like Duardin, the ability to walk along walls and ceilings! with special gripping apparatus and they could have a crazy subterranean submarine! They'd be utterly consumed by precious metals, minerals and materials with armor covered in gemstones. Their sworn enemy would be the dirty Rat men!
That would leave the element of 'Water' to be represented. Although, as we all know, the only liquid a Dwarf is interested in... is Ale! This Battletome would explore the Drunkin Duardin! and could take design cues from the war-machine aspect of the race. The biggest, most bonkers war-machines ever conceived, all blasting thunderbolts, beer barrels and cannon balls made from water with horrible sea-monsters floating within. (That would be a hell of a challenge design-wise) Due to their close relationship with all things liquid, we could see Duardin fishmen! Flippers for feet, Zeus inspired bidents. Their armor would be all shells and crabs with bright tropical colors to contrast with their constant foe. The shadow Aelves.