I think it would be great just to include an option to adjust game speed. A number of games have a feature like this included. (In fact, the Total War games do have it - it's just that the slowest speed is still a little too fast for some people.) I personally think the marching/running speed is fine.

Of course, this still wouldn't address the casualty rates. It would be nice to be able to adjust this too somehow. The issue a lot of people seem to have is that, percentage-wise, casualties pile up extremely quickly, making it difficult to execute complex maneuvers before the melee is resolved. I would like to see head-on melees take longer, to allow for more maneuvering combat.