Having done my thesis on the Union Cavalry during the early portion of the War Between the States (through the McClellan period). I believe perhaps some light on period cavalry tactics might help. I do have a copy of Brackett's work on my bookshelf, along with many other cavalry references.
Cavalry in the United States was always deemed as "light cavalry." Never intended for the heavy shock methods of the French Cuirass. The 1st and 2nd Dragonns were (better known as the 1st and 2nd Cavalry to Civil War battle fields) were equipped to move rapidly and dismount in order to fight in thick (forested terrain). As was the Regiment of Mounted Rifles (3rd Cavalry). They were, however, also armed with heavy sabers to be used if needed.
When the War broke out the regular cavalry units were scattered so much that out of 6 regiments only 7 companies were available at 1st Bull Run. They were nominally armed with the traditional carbine/revolver/saber that was the typical load out at the time.
Many subsequent volunteer units had trouble finding enough weaponry and quite often only had 1 company armed with carbines per battalion due to shortages early in the conflict. Until production caught up to demand.
The straightforward shock charge was already known to be a thing of the past and was taught as such at West Point. A rifle armed adversary could decimate a frontal cavalry charge. As they did to poor Farnsworth at Gettysburg or to the 6th Regulars at Malbern Hill.
Instead the officers were being trained to use terrain and fight dismounted while keeping a portion mounted for quick strikes. In effect a regiment might keep 1 battalion mounted in action while 2 dismounted.
The best examples of modern cavalry warfare and what it would become in the Civil War are shown by Buford, Gregg, Sheridan, Stuart, Wilson, Forrest, Wheeler, and others. Move rapidly. Delay and possibly hold the enemy until the main army arrives. Scout the enemy and ascertain their movements whenever possible. And dream of finding that big wagon train.
If we want the game to go historical, we should have a weaponry option of the trifecta of carbine/revolver/saber. Yet perhaps make it more expensive. While keeping the other sub ideas less expensive so you can build up to it as they did in the War itself.
Increase the power of a charge at the flanks or rear while keeping the frontal charge suicidal. Woods are best to fight in dismounted for cavalry as the tactics said to do.
The only thing I would really like to see is improved rate of Fire and power in the carbines to make them more realistic. The Spencer should be a savant, yet it is woefully unrealistic as is the ability of the late Sharps mode.