Convert everything to CMYK using ColorConvert within your refine process template when you first refine your pages. Then when you make your VPS it will come out as CMYK.
When you start to run the VPS click the 'Color Mapping' button. Then select the spot color you want to omit and set it to 'Do Not Output'.
However I do not know right now if those options are available with RBA. I can check more tomorrow if you haven't gotten an answer by then.