However, the biggest problem with such proposals is that they lack a way to clear the timeout. That is waiting for cancelable promises to arrive, which I am working on but I anticipate being contentious due to many differing opinions on the best way to do them.
So my best guess is that if you did propose this to HTML people would shout it down on the basis of not being able to cancel the timeout, and you'd have to wait until we figure out cancelable promises. But it's probably worth trying anyway.
I'd agree that we don't need `Promise.p.wait`, but I think eventually, ES is going to need a spec for an event loop. Or at least an interoperable spec agnostic of runtime should be created somewhere, like the eventual module loader.