I've had a look at Gallo's implementation some days ago and couldn't get anything to run, as I have absolutely no experience with Unity.
Of course I have heard about Sprite Lamp. And what I have seen so far looks awesome. However, if I get it right, you have to paint 4 lighting profiles for every frame of an animation. This sounds like a lot of work. Hopefully, Finn finds a way to integrate it with Spine.
On the rotation problem:
I guess, you are working with normal mapped body parts animated in Spine?
I considered doing that, too, but as you say, the light direction is lost when rotating images.
My idea is to go with depth mapped body parts.
As i am working with png sequences as an output format, instead of using runtimes, my approach is to render the "diffuse map" and the depth map of every frame separately (just using different images in the same animation) and process the depth maps into normal maps afterwards.
Currently, I'm doing that in CrazyBump, where I can also see a dynamically lit preview of one static image.
I made a small gif of really bad quality:
http://s.gullipics.com/image/z/q/9/7s9e ... ormals.gif
A small tool loading custom skeletons and normal maps would be awesome, just like the "spine player" you coded, only together with a shader. I'm definitely going to annoy Gallo with this request.