Vertex color node
Use mesh's vertex colors to drive some effects (like blending).
Usually vertex color is used in engine in order to do dynamic material blending. It is currently hard to preview how your materials will blend together in substance right now because of the lack of vertex color input. This can be worked around by baking vertex color in a texture, but then you cannot preview your material blending on several different meshes.
The Substance Engine does not treat the mesh at all, so this has to be something managed by the shader.
Jacob Andersen commented
The possibility to use vertex colors (not the baking method) would be really useful for games development.