At first I was like, I like the missle crusier changes (though 6 range is a bit TOO good, seeing as a single hex increase from 3-4 would already almost double the amount of squares you could hit), but I have to disagree with destroyer changes:
http://en.wikipedia.org/wiki/Destroyer
Destroyers show up the tech level at around WWII, so imagine these are WWII destroyers. In that case, destroyers in this era were armed with anti-submarine charges, anti-aircraft guns, and light anti-ship weapons. LIGHT anti-ship weapons. They were pretty much incapable of shore bombardment.
Your Destroyers are monsters, with 6 range, 35 combat, they will be able to sit in the english channel and bombard Paris! They will tear apart entire Infantry regiments. I assure you, a WWII era destroyer could do none of those things. Battleships were armed with artillery that could do shore bombardment, Destroyers were there for anti-submarine and anti-aircraft duties.
Ok, now that I've finished reading you entire changelist, I'm not sure what to think of most them. For the sake of realism, I'm not sure if the game would still be PLAYABLE.
Some of these changes are simply not balenced. You reduce the cost of musketmen while increasing their combat power, AND give them a range attack? I understand that Musketmen are underpowered in vanilla, but the decrease to 80 cost and giving them a 1 range range attack should sufficent. Their combat should stay at 16.
Some of these changes don't make any sense, or at least are not well explained. Crossbows, Chu-ku-nu, and longbows were all changed in different ways, and longbow change of range from 2->1 doesn't make sense since they currently have 3 range.