AFAIK, there are two options for baking a matcap to polypaint, though I’m not sure either will be helpful to your cause.
The first involves creating a displacement map from your model, using it to displace a plane, and then putting a material onto that while exporting the result as a texture image. There’s even a plugin that can automate this functionality. This means the direction the baked material takes is based off your UVs instead of the mesh though, which probably isn’t helpful.
The second method is to use a series of screenshots along with Spotlight or Zapplink. This runs into the same issue you’ve found with the nature of matcap materials, where the direction is based off the normal of the model. Since you have such a simple material, a simple solution may be to mirror it. So you would export the front-view and project it back onto the model, enter a back-view, flip the material, and paint that. This will require some manual painting along the seams though. Visually it should look as you expect, but granted I have no idea what a draft angle analysis is, or if there is any importance to the numerical values of the colors used.
Just going purely off of your screen shot, I think an object space normal map could be a possible solution, as it deals more with directionality. You’d just need to pick the color channel that represents the direction required, and use it as a mask between the two colors. A quick level adjustment can be used to control how harsh the falloff is. And because the result is a texture map, the colors will stay locked in place regardless of how you move the model. [Example]
