It would be sweet to allow an easier transition/connection between child pages and master pages. I almost imagine them as two different objects with a master-child relationship like we’re used to in salesforce. It’s a little confusing to call them ‘master’ and ‘child’ in a salesforce context if they don’t behave the same way.
J. might weigh in here with deeper explanations, but there are some specific reasons we don’t allow you to reparent a page. Much like the transition from stand alone to child pages there is magic behind the scenes. We’ll keep the idea as a consideration for the future though.