I was thinking, the easiest way perhaps for developers to offer legendary tier upgrades for the cannith challenge gear would be to make a legendary version of the two cannith raids and place a sort of trade in option inside the end of the raid.

Any tier three level 20 cannith challenge gear +Enhancement Blueprints for whatever item it is (For example- Spare Hand Enhancement Blueprints)=Level 24 item.

Any level 24 piece +Improved Enhancement Blueprints for whatever item it is (For example- Improved Spare Hand Enhancement Blueprints)=Level 28 item.

Further more, through this, I would also hope that they offer the same sort of upgrade options for Toven's hammer as well!

Also, this would breath some new life into some already enjoyable raids!