My personal preference is for Bastianini to join Mav at Aprilia. Depending on Enea's performance in winter testing, he could add intrigue to the championship and increase competition between the manufacturers.
Regarding VR46, I get the sense that this is part of Rossi's pension plan from Dorna, and he's tasked his organization with putting Italian riders in the shop window. This would explain why he's turned down Yamaha satellite bikes at a steep discount. I'd imagine the Ducati are the most supportive of his mission, and VR's contracts with Dorna are structured to meet his objectives. After 2 decades in the premier class, he probably knows how to ensure no one has leverage over him.
Why does Yamaha keep his as a brand ambassador? Why indeed? He rides a Yamaha at his rider academy tests, but other than that, I'm not sure how he promotes the brand or its products. Maybe he's going to race an R9 in World Supersport next year?