V-Ray for Revit - Generate Matte Passes?

[jackbird]

Does anyone have a working approach to generating mattes in V-Ray for Revit? (or in ART, this is about saving masking time in Photoshop).

 

There doesn't seem to be a Matte or MultiMatteElement available in the VRay element list, and the architects are very reluctant to do workarounds like changing all the materials in a scene to black/self-illum white because of its impact on other uses of the Revit model.

 

One idea that we've been kicking around is to do something with Phasing as a sort of duct tape and baling wire version of 3ds max scene states, but I feel like there has to be a more elegant way.