Truly believe that would be a feature that would make Rails exciting again. Just like Rails made CRUD ridicoulously easy, I wish they can do the same with more client-side oriented apps. It's admittedly a hard problem
I really dig point #2. My only worry is the current state of security in Firebase.
great idea, i'm using pjax but have no caching built in, i'm not the most knowledgeable programmer so I'm not sure I can help you, but I like your idea and will check it out.