You can observe the parent model for changes and rerender the whole component. Its not a great solution (I’m not sure it will continue to work with routeable components, and it is fairly tightly bound to the parent) but it may be what you’re looking for.
// component.js
_modelChanged: function() {
this.rerender();
}.observes('parentModel'),
parentModelBinding: Ember.Binding.oneWay('targetObject.model'),
Another option is to turn off readOnly before setting the score in _changed