When you're talking to an AI, you can demand that they give you control of one of their bases, or you can give them one of yours. But what I wanted to know is, is there any way to do that in multiplayer when talking to a human opponent? Sometimes that could come in handy. Helping a weak ally for example.
The onyl feasible way is to downgrade a pact to a treaty and have them seize the base. Of course, one of you will inevitably suffer a reputation hit....