Everade
That's in the documentation as a Prefab, it's the only Unity term used. It's also appropriate as it's the for word for "Prefabrication".
Prefabs are a wanted feature, and personally I feel better than just Adding more Sprite types.
I know what Ashley says, but there are two key points
1. The core run time is going to remain the same. So limitations in the rumtime will effect final features.
2. Best is subjective to what Ashley sees as the best and right way to game design. However some times those views aren't industry standards, and inefficient game design. As examples, Sprite Object instead of Sprite Behavior(which uses image atlases). Behaviors attached to every single instance of type, where as behaviors are best attached on a per game object.
So all we can do is see how C3 turns out. I'm hoping for the best, and I'm hoping C3 will be the best. But that requires flexibility and responsibility for the SDK community developers, rather than Scirra determining the best way to handle everything.