Many people don’t even use coroplast in cages for fear of chewing-however it really does depend on the individual bunny. Your idea does sound great and cheap, for a bunny that doesn’t chew. I would place a piece in the cage and supervise him for a few hours to see if he shows any interest in chewing it.

Haha, I know that feeling. I avoided that by doing literally months of researching other people’s cage designs. I just typed in different keywords for the cages into google images and went through practically all of them. I saved images that I liked design ideas from and then compiled all the aspects that I liked into my own cage

I probably wouldn’t use contact paper, I’d be far too concerned about chewing. That being said, you could use it provided you used a capping on the cardboard. I used plastic “u” shaped channeling that slipped firmly over the top of my lino and plywood that seals the edges from bunny teeth. You could do the same with coroplast or cardboard and contact paper. This sort of thing, it’s used for plasterboard but suited my needs perfectly: https://www.bunnings.com.au/peer-industries-10mm-x-3-0m-plaster-casing-bead-trim_p0730601

Here’s an example where I was attaching it to the edges of the level. The black area by the opening is non-slip stick on stair grip. The glue was strong that the edges couldn’t be pulled up on the lino flooring, and I covered the edges with the capping. I just had to cut it to the right size lengths for each side and it protected the edges so well.