The issue I see isn't so much that Generals the way Tom envisions them can't work. Its that when a realm that plays that way comes up against a extremely dedicated and capable micro-managing general, they are at a disadvantage. Thus in the interest of winning conflicts their is extreme pressure for everyone to follow this path.
I am trying something different, and I will admit it helps that I have some of the best military commanders in my realm to rely on, even though that means I've got lots of competition for the General position. I'm trying to set the army up something like the Dorsai mercenaries from the Childe Cycle books. Under this system part of being a good Marshal is making sure that armies that will be affected by YOUR decisions are notified, and that you take their actions into account as well.
For example people worry about armies getting left behind if one Marshal decides to pull back, turning what could be a close fought battle into a significant loss. Now I'm not going to fall into the trap of being online for every turn change to make decisions. I have no interest in ruining my family life just so I can be online within a hour of the turn. The important thing is SOMEONE makes the decision to pull back and that everyone is notified. I empower the Marshal to do this. I'm under no illusion that I am somehow more capable to make the decision, so long as the armies understand how system works, then orders provided by any appropriate source will have the same effect.
I will stress though, that this system creates LOTS of paper work for the general. I need to communicate in detail the plans and strategies to the military council so that everyone has the information to make appropriate decisions. Hopefully a side effect of this will be that the good Marshal I have will actually feel like they have something more to do then parrot my orders, and that players that aren't experienced in the military side of the game will be able to jump in and really learn.
