Multisite solutions as nested sub-sites

[medical-hero]

It would be very nice if you could nest several blogs in one another. Thus, it would be possible to give sub sites other themes and / or to change the blog names.
For example, a family have a shared blog on the homepage. But the family members have their own blogs in the sub-directories with their own name and visual appearance. For companies this can be also interesting if the various departments or locations have their own blogs.
However, the main blog must disable the sub-directories so that no overlap is possible. The admin panels of the sub-blogs must not disturb the panel of the main blog. Either the admin panel is located in the sub-directories, or you can control all the blogs in one place from the main admin panel. In addition, there must be a user administration, which controls who can add or change something on which blog.
For a better understanding:
www.blog1.tld/
www.blog1.tld/blog2/
www.blog1.tld/blog3/
www.blog1.tld/blog4/blog5/
blog6.blog1.tld/blog7/

[nacin]

As subdirectories, this is particularly challenging because URLs can clash. We "solve" this by forcing a /blog prefix on the main root blog in subdirectory installs, and all other blogs are also one level deep. Implementing anything beyond that will require some intricate hacking that won't end up in core. (Though we will improve the /blog prefix aspect in 3.1.)

That said, this is entirely doable in subdomain installs. Feed it fourth level domains and it won't really flinch.