The robots should have some kind of "brain" on their own... Like an army. First they could scout your base, exploring, looking for weak points. Then they could set bases strategically close to those points.
Other option could be that they KNOW about you using tricks and different armaments...so, they adapt! Like obtaining resistances to some type of damages (with a limit, so they cant become practicly inmortal), or even, they could make retreat calls! Like, when you are aproaching a base of them, they could choose between respond to the atack or leave the base in order to not loose units, and with that, reinforce armies in other bases.
These are just ideas, but DAAAAMMN It would be amazing to have a true challengue apart from, obviusly, growing the factory in more efficient and productive ways.
