I think that a great feature for Polypainting would be to allow mirrored painting based off of UV coordinance instead of the standard x. Reason being this, I work on low poly and find that posing my character can influence some of the expressive nature I put into my work. Having a feature like this that I can assign a hotkey to would greatly increase workflow without having to use a morph target or set up and use TPose.
You can use polypainting with Poseable Symmetry (which is based on the topology of the model).
http://docs.pixologic.com/user-guide/3d-modeling/sculpting/symmetry/
Oh snap! Problem solved, thank you.