I wasn't aware that Odyssey supported Ambient Occlusion.
It doesn't. As I said, it's intended to be used as an overlay over the diffuse.
Also, I notice that the UVW seems to be missing some parts of the model (particularly the top rear of the helmet) Is this fixed in the updated model?
Yeah that was ye olde MDLOps failing to deal with unbroken UV edges. It should indeed be fixed in the MDLEdit compiled versions.