-T- Plateau, Yunnan, Sichuan, Gansu, Qinghai, Xinjiang would be on top of my personal riding list, OK, I am biased as I have been several times in the regions.
Might do a Shanghai - Sanya ride in 2013 with a Guangzhou / Dongguan stop-over but it's different for me as I run a business on Hainan Island and Southern China and that gives me a few reasons and excuses…...