It looks like building a minimal system that's non-foomy by design, for the specific purpose of setting up anti-foom security and nothing else.

Your link for anti-foom security is to the Arbitral article on pivotal acts. I think pivotal acts, almost by definition, assume that foom is achievable in the way that I defined it. That's because if foom is false, there's no way you can prevent other people from building AGI after you've completed any apparent pivotal act. At most you can delay timelines, by for example imposing ordinary regulations. But you can't actually have a global indefinite moratorium, enforced by e.g. nanotech that will melt anyone's GPU who circumvents the ban, in the way implied by the pivotal act framework.

In other words, if you think we can achieve pivotal acts while humans are still running the show, then it sounds like you just disagree with my original argument.