A smart idea would be adding difficulty settings as well to keep beginners from leaving to quickly. The difficulty kind of spikes at the end two if you don't know how to play well.
Another idea for different game modes is an option for instance endless, timed, base, or modified.
It would also be a good idea to add more structures and mines (if that is even possible), maybe a structure that blocks abilities for a amount of time(probes sent) or it could be a mine