Hi John Wynne - we just showed pinning news for the first time at #MSIgnite18 - which translates to "coming in the coming months.' And "save for later" on Web is now out (and you probably knew that before this "sorta-late" reply.
And know that we take the "grow up from hub sites" story very seriously. We're putting the stake in the ground that people can and should build their modern intranet on SharePoint in Office 365 (with this new resource as a start with the what's possible today: ; plus roadmap items that further the story in the coming months (audience targeting for news/pages, improvements to navigation (mega-menu, audience targeting/trimming), a more parent navigation element, improved root site experiences, ...). And know that any site can be lightly linked to from any nav, just not officially associated which brings connections that are hard if it were to be associated to more than one, beyond a link in nav.
Cheers for now - always more coming,
Mark