The problem with Gavilar's unity of Alethkar was that it wasn't based around anything except Gavilar, Dalinar and Sadeas ctrushing the other highprinces into submission. A kingdom built on blood would easily break apart (and as we can see from Kaladin's time in Amaram's army, it already is). What Alethkar really needs is something to unite against. After all, Alethkar culture all the way to the Alethela is based around war, what better way to get them all together by having a common enemy? Of course, as we saw on the shattered plains, the highprinces are still very much separated. At this point, we just bring in Dalinar Kholin (who in the thread is referred to as Honor's chosen leader, or something like that) to become highprince of war and finally, properly unite them.