i think the current system is fine, because the distance issue represents the desire for autonomy. it also gives a scope of the extent of to where the dwarves lived at that time (the whole of the misty mountains, if i'm not mistaken). when i play i treat the two sides as different factions anyways. the east is slowly but surely taking back the east side of the misty mountains while the west is preparing to move south to help the allied high elves eliminate the greedy free folk of eriador
. eventually, though, the dwarven clans will be reunited under king dain, his lord thoring, and gimli, the lord of the west. BUAHAHA
i do like your ideas for new units, especially the cavalry and archer mercs you suggested and the wanderers, maybe make miners more of a very low-level shock-troop
EDIT: it's not like it isn't a good idea, it's just all the dwarves (the organized ones anyways) all had the goal of reclaiming moria and ousting the orcs from their former home. it makes it more...epic that way, to see how split the dwarves are