3rd RAJDHANI from SBC via UBL,PUNE will not materialize due to distance constraint. I think you have suggested a very good train in VSG - NZM RAJDHANI. Goa being a state must have a RAJDHANI. I think it should take the route of TVC RAJDHANI from MAO to NZM. However the slot is empty for the remaining 4 days. Even this can be Tri-Weekly train just like TVC RAJDHANI.
I think VSG - PUNE via MRJ would be better choice. As far as people of Karnataka goes, KSK via UBL should be made daily now that it doesn't share the slot with KSK via KCG.