In my reading on the Civil War the subject that is notable by its absence is the discussion of the use, impact and perhaps misuse of the Staff Officers. At a time when European armies, like the French and Prussians, have already identified challenges to the staff when directing large armies in complex battles and set up staff colleges to train dedicated staff officers, the United States hasn't. Maintaining a small army during the early nineteenth century, through both the War of 1812 and the Mexican War, these lessons were never learned by American officers even though the likes of Lee, Joe Johnson, McClellan and Beauregard had served on Scott's staff in Mexico. In fact their experience suggested they required only a small staff to communicate in the field.
Does anyone know good studies of the subject or have views of their own? Is Gettysburg a disorganised shambles for the Confederates because Lee has too small and inefficient a staff? Does Chilton need to be handed a pistol and given some privacy for the loss of Special Order 191 - a staff officer's worst nightmare? How much of Grant's reputation belongs to John Rawlins? How much of the credit Hooker gets for reorganising the Army of the Potomac after Fredericksburg belongs in reality to Dan Butterfield? Are the successful generals the ones who have the best, most effective staff? Are there unsung excellent staff officers buoying the reputation of average generals...? Discuss...
When the wheels fall off in a battle we never ask "how has the order, formed in the general's mind, been transmitted to the recipient officer"? Is it written? By whom? Is is verbal? Does it have both written and verbal elements? How is it delivered? By whom? Is it made by reference to a map? Who's map? Which idiot introduced the word "if practicable" into orders and what did it mean...?
This is an interesting topic, and not something I have personally seen specific studies on. However, as you have indicated the roles of staff officers can be significant in the success or failure of their generals both overall and even within specific battles. We can also see the role of staff officers for Rosecrans at Chickamauga with the fatal orders to General Wood. Despite the significance of the role there are also a number of examples of senior generals that have friends or family members on their staff. Meade has his son to his right in the photo here.