Gregory's ServerI think, to a degree.
Rather than having to reiterate the existence of user A, as in, userA has userA@mastodon account, a userA@loops account and a userA@pixelfed account. They're all interoperable in a way but not like a nested parent/child dynamic. Much like domains.
userA.pixelfed.loops@mastodon_instance
One would be control, depending on main use, but all would be accessible unto the parent without outward reach.
The more I try to detail, the more I think it isn't all that important. Since, I imagine, most would choose the style of content sharing they want to be the biggest part of: microBlog, shorts or pics and remain within those environments.
For me it's more about resources, not weighing down Mastodon with pics and vids, but also not having to create separate sm accounts just to do it.
Which, is probably a job for a good cms. I'll probably start playing with that angle I guess.