Blatant liar, what happens when a student in a C172 or Warrior;
(a) Stuffs up radio frequencies and misses a jump call, or
(b) suddenly diverts into the area due cloud or mechanical malfunction or being told by Essendon tower to remain OCTA, and
(b) Melbourne Radar misses the potential conflict through workload pressure, or
(c) The jump aircraft misunderstands communications?
As pilot of the jump aircraft, you are relying on Melbourne Radar and the actions of an unknown VFR pilot to keep your jumpers safe.
My understanding of the Reason model of accident prevention is to prevent the holes in the Cheese lining up by as many means possible. What I am concerned about is that you are relying on a positive action by a VFR pilot (to divert) to keep you safe. This introduces risk because if the VFR pilot fails you are in trouble. If Melbourne radar fails you are in trouble.
The chances of both failing at the same time (holes lining up) is not zero, better if the DZ was moved.
And on a personal note, if I'm inbound for a city orbit at Albert park from Moorabbin and the Tower asks me to wait, as happens frequently, then I'm orbiting right through that drop zone. The Hobsons Bay area is already crowded and a mid air is just waiting to happen.