One of the things I liked about the De-embiggenify quest early on is that you get shrunk down into a tiny Glitch. It's a reminder that the game's dreamlike state doesn't need to work on normal scales.
So could we have more of these? Entire districts or levels that are hidden inside other ones... or what about ones that are huge? I was thinking about a district built on top of (or inside) a gigantic statue. Lots of climbing and clambering up a single enormous structure.