A general note: I'm not really taking a stand on the importance of a singleton, and I'm open to the possibility that the only way to achieve a good outcome even in the medium-term is to have very good coordination.

A would-be singleton will also need to solve the AI control problem, and I am just as happy to help with that problem as with the version of the AI control problem faced by a whole economy of actors each using their own AI systems.

The main way in which this affects my work is that I don't want to count on the formation of a singleton to solve the control problem itself.

You could try to work on AI in a way that helps facilitate the formation of a singleton. I don't think that is really helpful, but moreover it again seems like a separate problem from AI control. (Also don't think that e.g. MIRI is doing this with their current research, although they are open to solving AI control in a way that only works if there is a singleton.)