RTS looking for Free Hobby Programmer

Yes it’s all BP. I’m looking for a feature where when you place a town center it creates a circle border live civ five around it. But this border also has to be able to be expanded with a paint brush like feature in which you paint the area you wish to become your land (much like the zoning tool in city skylines). Most buildings have to be built within this zone, however stuff like watch towers can be built outside. Thank you for replying