Yeah, that's the overly complicated and expensive thing that only a few thousand city carriers got. The bottom part rolls out of the rear like a giant drawer.
What i've got in my head (and need to get into SketchUp) is only as wide as 1 waffle tray length or maybe 2 waffle tray widths, dropping to one waffle tray width at the passthrough door, and is basically just a wire shelf with a 2" lip on the inner side, and some ropes to pull trays forward. Like, $300, $400 max for the prototype, possibly twice that if I decide it needs to be one of the fancier ideas (like two levels with the upper level being able to shift down when the lower level is empty, or a truly insane three level "rollercoaster" track like thing that I don't think I could ever make both functional and cheap...)