If the procedures are as I expect:
Scenario 1:
D/E or G boundary @ A025
IFR Jet ready at Broome for departure.
VFR aircraft is overflying @ A025 so operates to E or G procedures.
VFR is monitoring the centre frequency and announces if in conflict.
Departing jet has to give a departure report on tower frequency to receive instructions to change to centre frequency.
By this time jet contacts centre it is already though the VFR aircraft's level.
Collision avoidance is therefore reliant on MK 1 eyeball and ACAS.
Scenario 2:
IFR Jet inbound to Broome.
VFR aircraft is overflying @ A025 so operates to E procedures.
VFR aircraft hears descent transmissions for jet and announces if in conflict.
Scenario 3:
D/E boundary @ A025
IFR jet ready at Broome for departure
IFR piston inbound on descent through A040.
Tower cordinates clearance with centre. Departing jet is held on ground until piston twin has landed. Some delay.
Scenario 4:
D/G boundary @ A025
IFR ready at Broome for departure
IFR piston inbound on descent through A040
Each aircraft is given traffic on the other, but they are on two different frequencies. One aircraft is climbing, one is descending. WTF happens now?
Personally I think A025 is too low for the boundary between D & either E or G because (a) it doesn't give VFR aircraft to assess whether they are in conflict and respond and (b) aircraft B050 do not have to maintain hemispherical (or is it quadrantle) altitudes. To me it seems an A050 boundary seems more logical providing the size of the zone encompasses the airspace normally used by instrument approach and departure procedures.
DogOne:
1: E vs G VMC minima:
In E 1500m horizontally, 1000 feet from of cloud.
In G below A030 or 1000AGL in reduced VMC allows operations clear of cloud providing monitoring appropriate frequencies.
Do you really want a VFR aircraft legally scud running at A025 through the middle of your instrument approach?
2: E vs G radio carriage requirements
In E VHF radio with appropriate frequencies required by all aircraft
In G NO RADIO REQUIRED by aircraft B050 in normal VMC (I can't see a CTAF being introduced around the D let alone CTAF(R) - defeats the purpose of the tower in the first place).
3: Transponder required to be fitted and operating in E, only required to be operating if fitted in G. (I know this is relying on ACAS)
4: My scenario 3 vs 4.
My understanding is that procedures are identical for VFR in E & G. Given the above four points how is it possible for G to be safer than E?