So I've been reading Carl Von Clausewitz's famous book of Military Theory "On War". Its a very thought provoking book with lots of inspiration for game design. I'm only 500 Pages in so far, which means these notes are a incomplete/ Rough. I actually had already created by game "War is Not Chess" before starting to read this book, but I immediately saw how I could make a fun (and more involved) variant using concepts from the book.
Go to War is Not Chess to read the basic rules of the game.
Here is what I have so far.
1) Modeling Friction:
At the beginning of your turn you roll a dice under a cup. After your first action you reveal the dice. The result shows the maximum number of actions you can take this turn. As an example, if your faction normally allows you 3 actions (2 normal and 1 from your leader) but you roll a 1 you have already taken your only action for this turn. This represents all the things that can make orders not arrive on time, get misinterpretted, or even ignored. I actually think this variant is pretty exciting and would be perfectly fun to play in a normal game of Not Chess.
2) Archers are replaced by Cannons, Men at arms are called Infantry, Horsemen are called Cavalry
Cannons: like Archers but they have a facing. (Wrap rubber bands around the rook for friction and put it on its side to indicate facing). They can only hit the three spaces 2 away from their facing. They can change facing 1 degree (8 degrees around the square) before or after fire (but lose 1 accuracy if they fire on after changing facing). They can fire in the space directly in front of their facing as well (but only if they didn't change facing this turn). Also, if there are no pieces in the way they can hit the spot directly 3 away from their facing.
They have -3 to defend, but enemy units are lost if the cannon manages to win a combat as the defender.
Much higher attack bonuses though.
1d6 +1 for being a cannon.
+1 if there are no friendly units anywhere in front of it.
and an additional +1 for each cannon that can hit the same spot (though that cannon can't attack this turn if another cannon received the bonus from it).