I think you’re making an awful lot of assumptions here. This really boils down to the question of why someone would force all their users to change their URLs unnecessarily.
The original poster obviously wants to preserve existing URLs for his users; I’d guess that’s so all the links and bookmarks they may have out there don’t break, but really, we don’t know why and it’s not really our concern.
I’d say not forcing this change is a good thing. If his users want to change their URLs, they can choose to on their own. This is why I still have some tilde-username sites on my own domain, and redirects for others. I don’t understand why you insist that “he’s going to come to the point soon or later”. Why would he? I’m not aware of any inherent time limits on URLs.
For myself, I had a tilde-username site on my own domain for many years because I was running my own servers. When you’re doing this, and have given accounts to other people as well, the most natural way to set things up is for everyone to have ~username sites. The root site of the domain had a little information about the operation, services I was running, and a list of links to current users. No additional domains required. These users (including myself) were all, by definition, users of this domain/network/servers. This was before vanity domains became popular and it was years before I was ever asked to host additional domains, although there was no reason I couldn’t have from the beginning.
The status heirarchy you posted is strictly your own opinion. In fact, it used to be commonly considered a status symbol to have a site at a well-known existing domain (see The WELL, for example, and all the user sites they still host). But most people I know assign no such status based on something as unimportant as personal web site URLs.
EDIT: Well, the OP posted a follow-up at the same time I was posting this, so now we do know his reasons, which were just as I assumed.
If you want useful replies, ask smart questions.