Roughness Option On Subsurface Scattering Shader

Currenntly the subsurface scattering shader is using Lambert reflectance which is only accurate for perfectly smooth surfaces which could, but don't exist. What im proposing is to add a roughness slider which causes the subsurface scattering shader to switch to an Oren-Nayar reflectance when the roughness is above 0. The diffuse shader already does this.