One issue that has occurred to me is that both Maria and Joseph are very much the primary roles that the shows have hung on. And both Connie and Lee Mead were/are purportedly being very, very well paid to continue. But Nancy isn't a primary role, and the show (particularly when with Rowan Atkinson) isn't going to be as effectively reliant on whoever wins the role. So although "Oliver" is already guaranteed to make big profits, and the pay will still presumably be well over standard, I am not so sure that the same sort of financial incentive to stay on will apply.
"guaranteed to make big profits"????
In no way is this production guaranteed to make any form of profit, let a lone a big one.
There are few, if any, guarantees in the industry when it comes to profits. It is a high risk, extremely speculative game. Paul Elliott is on record as stating that after 40 years of producing he has just about broken even - the highs and lows, losses and gains cancelling out one another.