Chevy had a great idea with the Avalanche (that they've brought back with the Silverado EV). It had "saddlebags" - lockable waterproof storage on either side of the bed which Dodge copied with the Rambox.

The big feature though is the midgate which allowed you to open a panel from behind the back seats to access the bed and effectively converted the truck into a single-cab with an 8' bed. Great thing about that feature is if you had something that slid to the front of the bed, you can get to it through the cab.