The runway change has been in operation for longer that I can remember (over 30 years), there may be an agreement between HAL and the local authorities, I’m not an expert. It does require a bit of effort but at some point, aircraft have to taxi to the other runway and wait for the changeover, at some point, there has to be a slight “pause” to effect the runway change.

Unless it’s quiet, the usual time that it takes from pushing off stand at T5 to take off on 27 is somewhere in the region of 25 minutes, maybe longer during runway changeovers. I would question your comment on delays up to 60 minutes occurring during this process. British Airways has a regular meeting with representatives from NATS and if flights were being delayed by 60 minutes because of this operation, they would question it. The delays might be down to other reasons.

Your perception is that it is never smooth but from an ATC perspective, it’s a standard procedure that works well.