Hopefully the experts will buy into this one viz., OzExpat (procedure design) and Overrun (airports engineering). While OzEx has put a pragmatic viewpoint above, perhaps some detail on the protected areas etc in the final section of the approach as modified might be illuminating ....... and, if the not so good vis case is considered, perhaps worrying ?
(a) The usual story with a displaced threshold is that there is an infringing obstacle on the approach which causes the displacement to be necessary. Airport runway design standards require that the obstacle clear approach angle be not greater than whatever depending on the classification of the runway. The numbers aren't so important for the pilot as much as knowing that there is an obstacle protection built into the runway landing threshold position which is appropriate to the aircraft and operation.
(b) With an ILS, the fan section GP makes the situation better than with, say, a T-Vasis (remember those, Slash ?) but, for a significant displacement, the aim of using the first section of the runway is not compatible with following the displaced ILS anyway ? .. and that gets us into discussions about unstable approaches which are not nice at the best of times ... especially if the conditions are not good.
What it really comes down to is how far do we push our luck ?
If the practice is subject to a rational assessment and management protocol ... ie
(a) airports engineering people provide a technical assessment of the obstacle problem
(b) some sort of sensible operational risk analysis is made
(c) the regulatory authority authorises the practice
(d) suitable training exercises, to the extent appropriate, are embodied in the operator's programs
then, fine.
However, one must be concerned about ad hoc, non-standard operational practices .... which is what I read into the story .... eventually it can get to the same sort of situation as unplanned airshow displays with an attendant unacceptably high level of risk.
Then again .... you could always bring me, OzEx and Overrun up to do a study on the problem ........