I'd keep Ricciardo, not so sure about Vergne. His qualifying performces this season have been pretty dire, he's in the group of suspects likely to not make it out of Q1 along with Senna, Massa and Kobayashi (and the 3 'new' team's drivers of course). Over the race distance he has matched Ricciardo, however when moving up the grid qualifying pace is more important IMO. Hence I'd get da Costa or Frijns in.