Cover would be great.
Maybe they could do something like hiding. Press a button to show vision cones and diff colors for items based on the level of cover provided (half, 3 quarters, total). Obviously the enemy may choose to move which could change the angle of attack, but sometimes they wont or cant move position.
One way to implement the ready action is to delay your turn at the cost of your reaction, so you can wait for the enemies to come into range etc.
