Sound interesting. A few problems though. Pu erh tales many years to age with a CONSTANT amount of humidity not just a 30 minute 70% per day. It could takes over 10 years with that method. Build a puidor as I did, If you are really interested in aging pu erh. When I was reading about building humidors, I read a lot about cigars, one expert said to NEVER EVER use the method you mentioned above. Bottom line I wouldn't do it, and not to be negative or anything, but I think you are setting yourself up for disappointment. But hey, go for it! It will be an interesting experiment.
Hope this helped, and Good Luck!