Artillery based AA guns – ha, brings backs memories 😄
Of course you still have to factor in limitations at two per side or distribute them equally to both sides at the beginning of the game. Changing units stats and/or adding in new units are the surest way to expand the game into a new field of tactics and dynamics. This frees up a considerable amount of complexity and difficulty of altering the game board itself (too sticky), adding in totally new rule sets (too difficult to learn), or using dinosaurs (too extinct). Interested to learn, if anybody else has variations on different units.