One of the issues as stated by the OP was that there appears to be a lack of "action" by the players.
While a defensive bonus makes sense historically and works well as a game mechanism in combination with the economic/quality balancing, the downside is that it tends to discourage offensiveness in general. If overwhelming force is required to win, then no one will attack until they can assemble overwhelming force – and that makes the game bog down.
I guess most players are more conservative, building up a superiority in power before attacking.
In real life, in many cases, political considerations forced the politicians to demand offensive action before the Generals felt they were ready.
Is it possible to cobble up a routine that penalizes a player who does not fight? A governer loyalty hit, loss of victory points, British/French/Other diplomatic hits?
Each player has an "Aggressiveness" point pool. Small fights, entering an empty enemy province, and seiges generate a few "aggression" points. Engaging in a battle with/against
X number of enemy brigades, Naval fights (which were more "headline" grabbing...) earn you a few more. These "agression" points go into a pool. The pool will decay over time. (The pools in the very first turn of a game will have 0 points, so the first turn needs to be immune from penalties...)
A pool of zero (modified by year? By 1865, the Union needs to be Aggressive with a capital "A"...) causes some penalties to be suffered.
A player initiates fights by moving into a province containing an enemy force/fort, and engaging it. (The player must be able to be considered conducting an offensive in friendly territory, when repulsing an enemy invasion/incursion.) As it is, the computer generates the turns course of action through initiative rolls, I think. Therefore, you might be able to figure out what roll was used to determine who started a fight in a given area, and earns credit for that.
Thoughts?
That said i would like to see raiders added as that may give the CSA a naval element where they can raid like partisans or raiders do on land, though just destroy resources of the union. That would make the CSA player have a naval component to manage (other than blockade runners) while the Union would have to invest in a navy to try to hunt down these privateers.
One addtional scource of income (similar to the CSA's ability to get blockade runner goods) would be these raiders.
There is a given pool of trade (the Commerce pool) out there somewhere, up for grabs. By default, it goes to the Union. The CSA gets some with (successful) raiders. The Union doesn't seem to be able to do much about the blockade runners, but Commerce raiders should be closer to regular ships, where they can be seen on the map, and ships vectored to intercept them. The CSA sets them to operate in various coastal waters (bonus to rewards for operating off the north eastern USA, less so off the coast of Texas).
Raiders can fight as regular ships (and if they win, they gain a bonus to diplomacy rolls, a percentage of plunder from the Commerce pool, victory points). If the Raiders end up in an empty coastal province, they earn some plunder only.
What's in the pool? Money? Horses? I guess we can use the blockade runners reward system to determine how much is in the pool...
The difference between blockade runners and commerce raiders:
Blockade runners are gaining trade from a seperate pool for the CSA, and are near uninterceptable. Built for speed, not combat.
Commerce raiders are trying to hurt the Union's trade, and earn prestige (and diplomatic recognition) for the CSA. Better able to stand up to Union warships than the blockade runners, but they are still not as strong as a full fledged warship. (Max out the potential weapon upgrades to be less than the regualr warships can do.)
Thoughts?