Ability to make the # of Guests field mandatory for reservation types that allow guests

We have a reservation type called Doubles With Guests (separate from Doubles which is for members only) that allows a minimum of 3 players and a maximum of 4 players.  With any reservation types that allow guests, we want there to be at least one guest specified and accordingly, we would like the #Guests field to be mandatory.  This will prevent people from bringing a guest but not specifying the guest on the booking and therefore not paying the guest fee.  Given that not all clubs may want this field to be mandatory, having an option to specify whether it is or not (sort of like the fields on the CR Signup form) would be great.