Proposal/Request: Decouple coat roughness from transmission/refraction

[sharktacos]

Is there a means to decouple specular roughness from affecting transmission/refraction? In the Standard Surface, this could be accomplished with coat roughness which did not affect the transmission roughness. In Open PBR the coat roughness appears to affect the transmission, as does the specular roughness. I would wish that the coat did not affect the transmission so for example one could create scratches on a transparent surface without making the underlying substrate into (expensive to render) frosted glass.