Ability to specify full Custom Costs for true guests on reservations.

Right now if a club has different pricing for prime time vs. non-prime time, we don't have a way to reflect that pricing for true "Guests" on reservations. Was thinking we could add an actual "Reservation Guest" option as one of the columns alongside all the real Membership Types on the Costs Screen, rather than having it be just a single value on the Reservation level.