A very interesting addition would be unloackable formations, where when you place units on certain tiles in the layout screen they recieve different bonuses. Obviously they wouldn't need to stand on these tiles for this bonus, they simply need to be placed in that formation to recieve them.
Things as simple as +x or x% attack, defense, initiative, or things as complicated as 'If a life master is in the tile the army recieves +1 tactical health regen' Feel free to go nuts with this suggestion, or make it as simple as being able to choose where my units start in combat. The most important part of this being:
Let me put Verga in the front Row!!!