Just have each level (or set of levels) be set in different cities or even just vague regions representative of various countries. Could allow for a bit more variety in level themes and designs. Would be a nightmare making all the different models but if they stuck with the same simple art style it'd maybe be doable...
I just finished Reroll and I just want more Katamari...
---
This user is awesome!:
https://gamefaqs.gamespot.com/user/gamefaqs-user?account=12351915135