win zones seems to be abit like finishing with the previous level, area transitions however would allow you to go back to older maps if set to 2way transitions from 1 map to another, also allowing for entering and exiting buildings without duplicating maps.
biowares aurora engine (old now) has this feature and its excellent, you have a area transition wizard that helps you pick what map to start from where to transition to and how to get back to a previous map without much hassle.
if lee can do something like that it be awesome like skyrim or fallout 3/new vegas.
have fun stay safe
hood