So currently CVE assignments require a URL.
My proposal is that, simply put, if the CVE itself can contain all the needed data why not remove the requirement for the URL. The advantage of this is that for embargoed issues we can immediately submit the CVE to the database without having to wait for REF URL's to be created. The other advantage is that the REF URL can't disappear, the data is embedded directly in the CVE entry.
The common case is that in the OpenSource world we often have all the information needed for a CVE assignment, specifically in the form of a patch with notes, but that patch has not yet been committed, and it may not be a deterministic URL once committed (if we knew the URL in advance we would simply put it into the REF URL). This is especially true for Linux kernel commits and many other projects that use git. Often times as well these entities do not publish a security advisory or anything beyond "here's the patch commit with a note" (which is sufficient information in almost all cases).
So I think simply put if the rules are changed to include a statement such as: