Wordpress plugin modification

I would like an overhaul on how our postcodes are accepted.

Currently a selection of postcodes (listed back end) are accepted and the rest rejected. Once accepted a customer can proceed to our automatically displayed menu (something that changes every two months). Selecting a certain date then brings up the correct menu and selecting can begin.

I would like to be able to offer varying delivery options (different times on a particular day) e.g. Thursday 7-10:30pm for selected postcodes or "VIP" postcodes within the list back end. Meaning that the additional time slot is not visible for all our customers - only ones that reside in a particular part of our delivery zone.

I would also like additional postcodes that don't necessarily live in our delivery zone to be able to see our VIP delivery slots but not the normal ones. This is so that somewhere outside of our delivery zone can begin ordering but force the customers from that area to order all at once.