I'm trying to wrap my head around this new trend toward decoupled content. Maybe somebody with experience on it's capabilities can help with a scenario I'm thinking of.

The general idea of decoupling is that Drupal could be used as a 'content repository' that is pulled into several different architectures. For example the header and footer and such are a java app, or a mobile app, or whatever. 

My question is, could we/should we do this with Drupal into Drupal? I'm assuming it's straightforward, using REST api, regardless of what location is requesting content from the repositorl. I assume we'd build a Drupal content base, decoupled from headers, footers, wrapper, whatever. Then our corporate Drupal site serves up that content when people go to the video page, or blog pages. Similarly, another site of ours that is used by clients and not the public - also drupal, could be used to pull that content. 

Before it's suggested...yes, they need to be completely standalone sites - not just different themes. 

Also... how does Drupal 7 vs 8 play into this? I assume 8 is better. What if the above suggestion is dealing with sites in two different drupal versions?