After writing several suggestions in this message yesterday, I discovered that what I was asking for already exists here:
I have therefore edited this message to reflect only the conveniences that I think are worth adding to what is already in place.
In the scheduler, when hovering the mouse over a day that contains one or more shoots, it currently pops up a box containing the data of the shoots(s) booked for that day, including the personnel. Now what would be splendid would be if it could show visually whether each personnel listed has (as yet) confirmed or not. Maybe a red exclamation mark could be displayed before each non-confirmer, and a green tick displayed before each confirmer.
As an extension to the above, when viewing the scheduler page (for a whole month) but not yet hovering the mouse over any day with shoots in it, the summary displayed in that square could have a red exclamation mark to indicate that one or more person that day has not yet confirmed. (It doesn't matter which person or how many are unconfirmed; one could then hover the mouse on that day's square to see who it is who needs to be chased.)