This is awesome! The runtime is super efficient. Just a couple of little things I noticed when checking out the runtime.
1) Data asset creation - It looks like it always creates in the "Assets/" folder. It'd be nice if it created in your currently selected folder. Super small thing but I can see it preventing some whining haha.
[MenuItem("Assets/Create/Spine/Spine Atlas")]
static public void CreateAtlas()
{
string path = EditorUtility.GetAssetPath(Selection.activeObject) + "/SpineAtlasData";
CreateAsset<AtlasAsset>(path);
}
2) Bones as GameObjects - Im not sure how inefficient it is to have bones as individual game objects. I think it would boost the flexibility of using spine in Unity. It would allow designers to add box colliders, scripts, and components to specific bones. AFAIK large numbers of objects is pretty minimal performance-wise. It's the scripts that run on them and the draw calls that impact performance the most.