Speaking of the old officer system... I really like the auto-promote system in HOI2 a lot. I usually remove some of the high ranking officers, and enjoy watching my commanders gain experience and advance in rank as I fight battles and expand my army, respectively. I would absolutely love to see some kind of development or expansion of this system.
I think everyone wants to keep the historical leaders. Theres nothing better than playing as Germany and having Rommel, Guderian and Von Manstein leading your armoured divisions.
But developing your officers is great fun as well, and the auto-promote system means that your officers don't lose skill or xp when promoted. The price is a severe restriction when attacking, as you never have enough generals and field marshals for your operations. It is this tradeoff that I love about the system. Also, you can't control who is promoted, which is great fun, but some degree of influence would be even better.
All in all I would like to see more like that. More events that customise your leaders, IN-style decisions about promotions. Maybe a loyalty-factor that can drop if the officer is passed over. Military reforms that increase the skill of some of your leaders but comes at a price. I don't want to take away the historical leaders' characteristics, but spicing them up with player influence would be great.
Anders