I feel quite lucky Charlie isn't a chewer
I guess some chewers will chew anything, but as you say it's just keeping an eye on things and common sense. In fact I wish Charlie would chew some wood. The only wood he will chew is if it has food attached to it like those chew sticks - so I get those Rosewood naturals ones.
There are a few examples of Knuff creations here!
Project IKEA - Platform/Level
Almond's IKEA Knuff house is finished!
This one has a picture of knuff shelves and also another Ikea hack for a house - although I wouldn't use the fabric mentioned personally.
IKEA Hack DIY Round Fryden House