I'm confused by this. There's still original characters in the new Paper Mario games they're just uninspired and bland. I don't see what's so difficult going back to something like Super Paper Mario for example which kept the Mario characters in line with the usual stuff but added a whole cast of brand new characters too.
I understand that while visually they have to be radically different to dissociate themselves from existing Mario characters (They are origami vs. 2D Paper), better with an in-universe reason to look different (Origami doesn't belong in the Paper Mario universe), they can't be a wild departure from the shared look of the Mario series (The origami-ed Mario characters look closely to their standard design).
- The office appliances are real-life objects that have personalities; easy to tell they're not part of the Mario universe: OK
- A green goomba with a different body-type, name, or hair: Not OK
- A goomba with sunglasses, when it makes sense in context (e.g. It lives in a desert): OK
- Origami variations of Mario characters: OK (Since they end-up resembling Mario 3D models closely, makes sense in context)
- Origami original characters: OK (Minimal, the context of their appearance is that they don't belong in the Mario universe, one-off)
- Original character that are said to be part of the Mario universe, but from an unseen part, and deviate too much from established artstyle: Not OK
It'd be so interesting to see the development, design, and legal documents for these games :v