I really like this Nohadon theory. Especially because it relates to Dalinar's trajectory. He's constantly being told to "unite them," but it's not until the end of the book that he realizes that he can't just hope for people to band together; he's going to have to force them together.
He realizes that Nohadon probably had to do something similar, and then afterwards he wrote the Way of Kings. If we follow the theory in the OP, the way that Nohadon accomplishes that was by dragging a Dawnshard to Urithiru and re-binding everybody to a new version of the magic system.
What if Dalinar is meant to do the same thing? Fix the magic system by re-binding it according to rules of Honor? Maybe it's the only thing that finally gets Szeth to quit trying to assassinate him, too.
Of course, where is Dalinar going to get a Dawnshard? I suggest that the original 10 shardblades in the prelude, abandoned in that rocky place, are the Dawnshards. That rocky place that could potentially be the original Shattered Plains.
Dalinar is conveniently located next to the Shattered Plains. And the Parshendi do everything they can to defend and hide the depths of the Shattered Plains... possibly because there's a bunch of Dawnshards sticking in the ground there.
So Dalinar, in order to unite everyone like his idol Nohadon did, will need to fight his way to the center of the Shattered Plains, get a Dawnshard, figure out where Urithiru is and how to get there, and then use it to bind everyone.
I like this theory because I can see how that would work as a story, taking our character through a lot of Chekov's Guns and also leaving lots of room for great action scenes, conflict, and myth-exploration.