Currently, Rash’s default stage is the same as Kan-Ra’s.
While some would find it appropriate due to the portal in the room, I still think Cinder’s stage would fit him better, as it emulates the Battletoads vibe much better (the lava recalls Ragnarok Canyon, the machinery and flying drones in the background resemble the more industrial/hi-tech levels). It even fits his theme song better.
Also, Kan-Ra’s stage is currently the most overused stage in the game’s Survival mode, being shared by 3 characters.
What do you think?
EDIT: Apparently Cinder’s stage as his default background was indeed considered at some point - it serves as his background in the official site’s Characters section (https://www.ultra-combo.com/characters/rash/)… Why the change?