I wonder what the rationale is for some of the fortifications, particularly the one south of Nashville and the three in Fredericksburg (wouldn't two at most be more accurate?). There also seem to be an awful lot along the Mississippi, whereas in the real war, Vicksburg was about the only significant fortification between Memphis and New Orleans.
I also disagree with having to besiege every city. Playing against the AI, I have to besiege every city in the South. If an artillery piece (whatever amount of artillery that is supposed to represent) and a few brigades were sufficient to hold up an army for weeks, then places like Nashville would not have been immediately abandoned or walked-into like New Orleans.
There also seem to be two many level 3-fortifications. Arguably, Vicksburg, Richmond, Atlanta, and a few coastal forts were the only places with extensive, formidable defenses.
Having said all that, I am certainly willing to wait for the next patch and withhold suggestions until we all see how those changes work out.