Nick Coghlan writes:
P.S. Given the existence of the constraints discussed above, folks may then be curious as to why we have a brainstorming list at all, given that the default answer is almost always going to be "No",
Besides providing a place that encourages discussion of ideas from out of the blue that just might be evolutionary steps forward, it also provides a place where language design principles can be discussed and illustrated in the context of concrete proposals, and an archive of those discussions. I realize that it's a significant amount of effort to find the discussions where principles are enunciated and elaborated, and don't have a good solution to propose to those who prefer not to spend the effort. But the resource is there.