So, in the vanilla game when the event "AI rebellion" occurs, the machines will live on the special "AI world" planet type, covered with artificial stuff and all that.

I'm imagining that there could be a feature that would allow an AI empire to either start of on an AI world and/or have the ability to "build" colonized worlds into AI worlds, and that this would grant the planet bonuses to various forms of production, at the cost of rendering it drastically unhabitable to any other form of life.