A few of points to add.
The first regards the actual position of the inbound point. The ERSA lists TWRN as S 33 56.2 E 150 53.3 and has a position for 2RN (in the NAV/COMM section) as S 33 56' 38" E 150 53' 10". The first thing to note is that radio transmitters in the NAV/COMM section are, rather unhandily, in AGD66 not WGS84. From my calculations that makes it S 33 56.5 E 150 53.2 which would put the radio mast south of the promulgated position for TWRN! I don't have access to a certified conversion program at home so I am more than happy to be corrected if someone can run the radio mast position through one. Either way they do not seem to be the same point which I find a little bizarre.
My second point regards the utility of the current reporting point system. In a CTAF you make an airmanship decision where to call depending on a range of factors such as speed, altitude, intentions. Thus in a high performance IFR aircraft I will call a long way from the airfield to give time for me and others to arrange separation. In the case of GAAPS the reporting points seem to be for ATC purposes. Not a bad thing in an of itself but it does not give any chance for establishing separation before reaching the choke point. In my opinion the inbound reports are too late for pilots to separate themselves based on listenout.
Thirdly electronic aids are available, but we need to find a way to get them on the street. TCAS, ADS-B, and PCAS all offer possible solutions to improving our SA in busy airspace where ATC are not providing separation. Sadly the plan to cross-subsidise ADS-B did not come to fruition so that is not an option in the near term but PCAS may be a value for money option. An earlier post suggested that TCAS cannot work in such a busy environment but I have been very pleased to have TCAS I in these circumstances and TCAS II with RA off will do the same.
Finally, Howabout, sensible question. Defined routes do reduce the chance of VCAs, particularly for those not familiar with the area as topo maps don't always show the most identifiable features in an urban area. This will have to be considered if any changes are made but it does not prevent changes being made to GAAP procedures.