Brent,
You mentioned having an ancestor in the 13th Indiana Cavalry. Dyer's Compendium says this command began organizing at Indianapolis on Dec. 23, 1863. After service in the Tennessee Valley in 1864, the regiment passed through Vicksburg MS in the winter of 1865.
Did I misunderstand, or were you saying your ancestor was involved in the Vicksburg Campaign of 1863?
From a reenactor's standpoint, it's important to accurately depict wartime events. If that means some Southerners need to wear blue uniforms, so be it. As a friend who spends many weekends as a reeanctor explained, it's inaccurate to depict battles in which a handful of soldiers in blue defeat a much larger body of Confederates. He asks, how does that honor my Confederate ancestor?