Hi, I am one of the developers working on this problem too.
I am wondering if there is any way to alter the GenerateMecanimAnimationClips method, so that it creates animation clips which are NOT child of animator controller? it would mean a lot to me if those animation clips are on the file system, and are easily accessible.
Thanks
EDIT:
I think I found a way to just save a clip to a file, rather than add it to controller. But I would have to change the method in Spine runtime, which is bad practice. I might do that temporary.