Covering Plastic Trays with Fleece?

I recently bought a ferret nation cage for my chin and it comes with plastic pans and shelves. Will it be okay if i completely cover the plastic with fleece liners? I made them such that they're sort of like a pillow case and covers the whole entire pan.



In addition, does she REALLY need the ladders? i mean chinchillas can jump pretty high and the shelves should give them enough height to jump from the first level to the second.