sorry to dig this up, gonna add some of my own observations.
i've gotten a customizable character working with spine, and the sprites are coming from SpriteAtlas and SpriteAtlas variants alright.
I've noticed a bug where spine isn't honoring the scale setting of the SpriteAtlas variant (was trying to make a low-res texture set for zoomed out views). it looks like spine is just grabbing the same coordinates from the atlas in absolute coordinates instead of some relative coordinate space like UVs. For example, where it should be grabbing one hand graphic, there's actually 4 hands, as if it's copying the original unscaled hand's pixels from the now-shrunk-atlas and accidentally grabbing nearby sprites
Presumably i need to tweak ToAtlasRegion to return the adjusted region?