I'd like to comment about burning large cities to the ground. I think that this is much easier to capture productive cities in my imagination and in the game than it was in real life. I don't know about every city, but take
Cincinnati as an example. As CSA, I nearly always take Cincinnati, often before St. Louis, and even in games I lose, it is just too easy not to. In reality, Cincinnati was defended very heavily during the civil war. Tens of thousands of militia volunteers (famously called squirrel hunters) were available and were called up in September of 1862. When Bragg arrived, the city was well defended by artillery batteries and over 50,000 troops in spite of a relatively small regular army force available. After September, dozens more artillery batteries were built. And the city was a prize worth capturing, of course (Eagle Iron Works produced some 2000 cannons during the war, a lot more than would be suggested by WS in the game, by the way). Maybe I'm quite wrong, and maybe Cincinnati is a special case, I'm not sure.
Once a city was captured, I agree it would be fun to have the option to burn it to the ground (reduce some structure levels, destroy others, not sure exactly what it would entail). I'm not sure exactly what the consequences should be, though. Cohesion of the occupying force should drop a lot. FI should maybe drop a little bit (it would be quite different to burn down an occupied city than to shell it - cities were shelled in wars in Europe too). I'm not sure what else, it would be tricky to get right.