That sounds like a great idea!
not exactly the same, but when I had my hamster in my room, when I'd go to bed at night, he'd run and run and run in his wheel. It drove me nuts!
I want Lola to be able to free range too. At the moment, she is under supervision, and then back in the cage at night. On the few occasions she has chewed things - like through my telephone cord - so I'm hoping once she's more well trained she won't.
I like the idea of the puppy play pen, to block off a few of the areas, though! Great idea!