...obviously this is a dream scenario for some and a nightmare for others but just say it happened, what would/should be the board's next move. Who would you go for?

Me, personally, I'd be all about Slaven Bilic. I think he has what it takes to run a proper sized club. Failing that, Thomas Tuchel. Not Bielsa, not Mourinho but maybe Benitez if he's freed up by the Geordie's pure abjectness.