The system where you click a circle, get some options on what you want to build on that circle, then pick structure of choise? Start with making every structures you need in your map, then create your circle of power, where you add all the structures you want to build in "Techtree - Upgrades To:" (found in object editor for your circle of power). Really it will upgrade circle of power to selected structure, but none will be the wiser. Personaly I have not experimented alot on this, but it shouldn't be a problem. Correct me if I'm wrong.