Not that I know much (read anything) about modding, but this era demands a Steampunk mod. Don't you want to see a group of Her Majesty's Air Ships demolishing the rebels over in the Colonies? Or what about clockwork armies of Napoleon Bonapart invading Russia? And what about the epic steam-powered tanks used as the two great German empires attempt to annex one another?
The new real-time naval battles, I think, could probably be easily adapted to Zepplin battles. And a more competent modder than I could probably figure out how to get them involved in land battles as well. Just a thought