Trying to hide exit nodes would have little effect on censorship. I believe a more effective approach would be just do the same the vpngate guys did to beat the chinese firewall. Just mix in the published list some essential or high popularity IPs (ex. DNS servers...) as if they were relays. That would send the censors in a goose-chase when a lot of people start complaining about the block. The cost to censor is raised considerably. They would have to check every relay address before adding it to a blacklist, or risk breaking popular services. It's just not worth the trouble.