The Pc's have been asked to join up with a minning company which is run by a junction of dragonmark heirs all which formed a partnership. They all work under and enigma who is funding the many expiditions who's plans for the comapy to become more then what it's origional job is to be. After a few meetings the two artificers will be asked to help develope some inventions of the patrons designs. The Inventions are a elemental powered rifle which is just a test to see how effective the idea can be, an earth elemental bound tank like design that can bring heavy weapons and troops into enemy held grounds, and a few other war type inventions which will later be mass produced and used in a new war.
Then the PC's will be given the option to either join the patron and help him fight or go against him and maybe try bringing the five nations together to fight this enigma...
Lend your opinions to the idea!
If that's not epic enough, have the immediate bad guys be Aurum who are being manipulated by whoever is really the badguy, that way you can have a fun time when the Aurum "masterminds" get their toys turned against them. Preferably at a good time for the PCs to witness their inevitable betrayal. Maybe the Aurum betray the PCs, but before the PCs get killed their unknown patron moves in to take the new inventions and betrays the Aurum. >.>
And having a mining company do it is a bit weird...
Generally if you're saying "elemental binding" you're talking about gnomes. Maaaybe Cannith if they're trying to steal the tech. It is possible that some sort of gnome rogue has stolen some binding schema's etc and is trying to develop something new and using the mining company as a front, but I just don't see anybody else developing something like that.
Let alone something like a "rifle" or a "tank" which are vastly beyond the current level of Eberron's "tech" (it's a fantasy setting, the ships may fly, but they don't have jet planes).
Hope that helps a bit...
Instead of guns, why not try to reverse engineer a creation forge from incomplete plans and produce a bunch of juggernaut warforged. Or maybe you could have some mostly retarded brass or earth golems. In any case, I think adding guns to Eberron's high magic, ruins its... well... magic.
Not because guns aren't cool, but tanks and rifles starts summoning up images of WWI and trench warfare and then with all that destruction in the hands of low level npcs, the adventurers are totally overshadowed. Thats the problem with guns in a fantasy setting. It takes time and effort to be able to kill somebody with a bow and arrow. It takes much less to become proficient with a rifle. It wildly changes the environment. I don't know if that's the road you want to take, but keep in mind the tone you want to maintain.
Also, if you want to play a game with guns, there are tons of other games that do it much better than just houseruling rifles into DnD.
Mind you all that my characters are still only lvl 5 and the actual events of the war creations won't show up till about lvl 15-20... its kinda like their created only to taunt then are destroyed...
Seriously.. I'm all for transporting drizzt and a kender into the game, (oh jeez.. now I'm gonna get flamed), if the dm thinks it could be fun. It's a game. Not a friggin bible.
But back to the question:
I'm with the Aurum as well. But back them up with another group that will double cross them. Just as mentioned. Instead of Dreaming Dark, I would take The Chamber or Lords of Dust. CHamber because: well.. maybe they WANT a war. That will spark off some major branch of the prophecy. And The Lords of Dust because the chaos of war gives them oh so many chances for furthering their own plots.