Great stuff. It looks like a ton of upfront work, but will greatly improve the standard, and shouldn't be too hard to maintain once it's complete.
That said, my overall point is that optimization does not rely on undefined behavior at all. It's commonly argued that it does, but there are languages without undefined behavior that have working optimizers, so it's clearly false. Some optimizations for C (and C++) currently depend on undefined behavior, but there's nothing inherent about that dependence.