Sounds cool! Don't worry about it too much though, the game is still solid even at scores above 20 million- though maybe less so if someone were a veteran snake player?
Rare characters could also have unique passives / new classes-
Various fun ideas:
- A character that goes to the front when added.
- A character that has a chance to pick up chests it walks on, even if it isn't at the front.
- A character/class that you want to be adjacent to a specific other character, but not to most characters- this would encourage players to make to make carefully sized pinched loops! Ex- it has huge damage buff when near to one class, and slight reduction when near to another.
- A character that, when you try to walk through it, places portals on either side of it, that last until the whole snake has gone through.