Wow I love the look of those labyrinth houses Pikachu would love one of those!
Pikachu started biting the plastic on her wheel and her platform a few nights ago, My Nan got her some fruit scented chews for Christmas and since I gave her one of those she's being doing it 90% less. Maybe that would work for you? You can home make the fruit scented chews if you have plain wooden ones, there's a tutorial on ErinsAnimals on how to do it
she also loves her crocodile which someone mentioned that brand earlier!
I bought her a new wheel though as it's only the wheel she is still biting the new chew actually stopped her chewing the platform, she has the Trixie so I'm thinking she doesn't like it being enclosed really? I have bought her the Wonderland in hopes that it stops her, but if she bites that then I'll have to remove it in case of splinters when she runs!