Cnames to convert something like .hidden to .onion is a decent idea. If nothing else, when people start clicking on links, and getting "unresolvable"/"No such host", that might give more exposure to tor to other people.
We could set up a DNS system entirely within Tor. Just have cnames from host.hidden.onion to somelongkey.onion, and it is never seen by the rest of the DNS world. The mappings would be registered with the directory servers, who would track known, registered mappings from host.hidden.onion to key.onion, and key.onion's would be registered as they currently are. We could even do a combo. Get a special TLD now, or add to an existing special, like .int. (approval time? About a week). Start putting in names, registrar being the Tor central directory servers. In about 3 months time, when the code is written and tested, move to Tor served names.