Give us a mutating level! At first, you’re in a relatively small but compartmentalized area - like a plane, ship or train. Then, at the 20~30min mark, the level changes because of some event (plane lands at airport, ship docks, train arrives at station) then the level mutates into a normal level of the smaller variety like Whittleton Creek - the aforementioned airport, harbor, station.
A couple of mission stories can be exclusive to the small section of the map. The rest are for the normal sized one. You’d have entry points that took you immediately to the bigger section (if you’re going for some challenge in the larger section) or for flavor.
This could be kind of cool!