Viks are actually Outcasts. They are mercenary however, which means you could if you wanted run them with some guild (I think this is only possible in a Brawl however, ie large scale game with 2 masters).
Better go for the Outcast models to complete your Viks crew, there's lots to choose from, the common choices being adding VonSchill and his Freikorps gang, or any of those unique models which are so great (Sue, MacTavish, Hans and many more...)
Good luck!