Verstappan and most of the big names fall under the CRB, unless Merc wants to spend huge $ to pay for both the driver and team he leaves none of the big names (Ferrari, Red Bull, McLaren, Renault) are going anywhere. Bottas is the one I suspect will be tapped, Wolff client, not expensive, Williams could benefit as a Merc client. Grosjean is another as he has an escape clause for a "top team" written into his contract with Haas. Both would be filling a short term gap until Merc either brings in a young talent like Ocan or hire a big name when his contract expires with another team.