Ember - or Backbone, for that matter - would be a bit trickier to write a plugin for. Neither really handles hierarchal data structures in an elegant way - both have a model layer that assumes a "flat" structure, similar to server-side models.

With Angular, on the other hand, you can just pop the full object from retrieved from the server into your $scope, change it like you would any other object, and then sync it back with a function that will create a diffset between the original object and the current state.