I'm still rearranging my itinerary for my DONE4, and I've been investigating other long-haul runs (i.e. over 2,000 miles in the BA definition) out of HKG. Apart from DPS and CGK, you could also fly to Surabaya (SUB) in Indonesia at 2,042 miles. Another one I haven't seen mentioned yet is Sapporo (SPK) in northern Japan at 2,130 miles. Perhaps the turnaround there would be easier, but I've never been there. Perhaps someone here will know...