My biggest concern is the higher levels... Specifically, Eberron (or, rather, Khorvaire) seems to "cap out" in the upper mid levels (say 12th-15th). Bringing in the dragons from Argonesson mitigates that somewhat, but really, I think the best option would be to get the forces of Xoriat or Dal Quor involved.
For that matter, it seems that if you're going to do an Eberron adventure path, you should really try to hit all the continents.
So here's the things I'd want to see in an Eberron adventure path:
*The Riedrans are on the verge of being able to unleash the full might of Dal Quor on Eberron.
*A group of time traveling giants who've foreseen this coming Quori invasion way back when have jumped to the future to fight them (and take revenge on the dragons which destroyed their civilization). Few in number and desperate, they strike a bargain with the forces of Xoriat.
*Many of the dragons of Argonesson are mobilizing, no longer content to observe the prophecy passively. Some want to try and rally the dragonmarked houses and other mortal powerbases to aid them against the Quori and the giants, but others feel the prophecy dictates that all non-draconic society should be wiped out.
*Meanwhile, that's all background stuff barely hinted about at first. The meat and potatoes of the campaign starts out with typical politicking. All of the events above send ripples through the world. The dragonmarked houses and the governments of Eberron all react to the ripples, not yet sure of what's happening, and the PCs get sucked in.