I've done this a couple of times on both award and paid (with and without charge). It's usually easily done, but have heard both views on the reissue charge. I was twice in London trying for a Y standby and both times they tried to charge me the reissue charge. They just try to put that on me for whatever reason.
However, also a good one also was when i was in London with my parents last week- had to leave 1 flight earlier for family stuff but Y was overbooked and J was soldout. They managed to get us 2 J seats and a points upgrade to F. So happy family for that.
HKG-TPE-HKG are quite easy to be done... I would imagine that to be the same for other short-hauls esp with status.