This doesn't make the problem of controlling an AI foom go away. The non-foomy systems in charge of the world would still need to solve it.

You're right, of course, but I don't think it should be a priority to solve problems that our AI descendants will face, rather than us. It is better to focus on making sure our non-foomy AI descendants have the tools to solve those problems themselves, and that they are properly aligned with our interests.