This is an interesting conversation, particularly because part of it centers around how Civil War leadership tactics evolved as field experience accumulated. This game has been out about 21 months now, the equivalent of almost halfway through the actual war, and players are still evolving their own strategies and tactics. That, in my opinion, shows the game's depth.
On the other hand, I'm not sure players should be able to benefit from the advantages of all-artillery or all-cavalry divisions early in the war. While I'm all for the freedom to explore historical alternatives, there is already a precedent for handicapping our advantage of 20-20 hindsight (the locking of division and corps structures, for example) to create a more historical simulation. So while I agree with Gray Fox all-artillery divisions do reflect the armies' respective artillery structures, I believe an ideal system would limit the player from adopting those structures until they became historical realities. I realize that a) this is not a major issue, b) that it won't (and shouldn't) be reworked in CWII, and c) it probably involves a lot of coding that might not be possible, but it is something to think about as these games continue to be refined and evolve.