I worked the radar sectors around PH for about three and a half years so I have some idea of what happens with all this.
It pains me to say it but Greg has a point. If 40 aircraft all want to depart from the one runway within 5 minutes, there's going to be a problem with delays at any airport you want to look at. Then, when there's 20 aircraft wanting to land on the one runway within a 5 minutes period (based on profile speeds), you're going to have the same problem. If you spread the FIFO flights out, you won't end up with the delays. It really is that simple. And it's not AsA's fault that this is the end result. They have no ability to improve any of the things that would help move 40 aircraft in 5 minutes. They simply provide the best service they can with the tools that they have.
The base cause of all the delays is not getting optimal use of tarmac on the ground. Put in a parallel (should be able to take at least B463/RJ if not B712) and make more use of 06/24. With these two things, the movement rate could very well double. Simple. That means, however, getting the people under final for R06 to quit whinging about noise and given how things are for AsA at the moment with the noise from WARRP, I imagine things would get very interesting with that. It also means WAC need to forego commercial ventures and use the airport for it's intended use - to move aircraft! Good luck with both of those things.
I have said it before - airspace is not the issue. On departure, the only weak link in the chain is from approach to enroute - approach are happy to run 5 miles between departures which is going to be refused by enroute everyday of the week. I was happy to have 7-ish with opening but the procedure says 10nm, no closing and when tower can launch them to give approach 3nm on departure, that means a bit of speed control to get the 10nm approach need for handover. The non-radar guys don't cause delays - they catch everything sent to them and just use levels to sort out any conflicts with the odd reroute to fix a real dilly of a pickle. If all the charter guys were to have adsb, the only improvement here would be that people would get their planned levels almost all the time.
On arrival, adsb would only help if PH TCU were to get the adsb feed. When I left 15-ish months ago, they had no feed and were not going to get it ever with the current platform (TAAATS). So adsb fit out for the charter fleet is not going to help with delays by itself. If the flow does get the adsb feed and the stations are at the right location (probably Meeka and Leonora close in), then the flow can do his thing from top of climb and help absorb delays in the cruise. In this case, if everyone sticks to their slot time, it will probably get rid of holding entirely. However, there is still only so much this can achieve. If those ridiculous days still occur when 40 aircraft all want to land in the one thirty minute block, there is going to be holding.