Anybody is capeable of wirting a sub class of AttachmentLoader: StarlingAssetManagerLoader
I often have a mixture of quite a few assets. Some animation assets some other. Also they distibute over a few texture atlases.
Of course that class would also compensate for the scaling of the textures.

var json:SkeletonJson = new SkeletonJson(new StarlingAssetManagerLoader(myAssetManager));

Would that be possible?