High interactivity and unpredictability
When I designed Tonkin I primarily wanted to have these two effects. I solved it by limiting each player to only be able to do 1-3 actions before the opponent did his actions. An action can be to move a stack or to remove a disorganized marker or a few other things. You never know beforehand if you will be able to do 1, 2 or 3 actions. Therefore it is difficult to plan which introduces an unpredictability.
Which aspect have you searched for when designing?