LAHSO - problematic cause some companies could not guarantee that they would use it. One uses 2300m in ML but wont change SoPs to use 2247m in Perth (03 landing). Only useful on 03/06 configuration and the nature of Perth traffic being what it is...most of the arrivals are the subsequent departures.
11/29 - too many taxying aircraft to ever be a runway again.
24 DEPS - taxyway structure would need a big redesign. = $$$ to be spent on non commercial infrastructure by WAC = never happen. Also the NIMBY factor in play. But if you could get 24 used by F50/Bras/DASH types and jets off 21 ...hmm. Then the delays would happen airborne as the jets caught the props but procedures could be designed with separate jet/non jet SIDs so the passing levels were reasonable and the tracks did not come together until about 30 track miles.
Also would need the RAAF to relinquish levels below FL160 for transit closer to the coast for off set tracking of the segregated routes. Been there done that ..failed!