My 2c worth.....

If anything is going to happen, the organiser/s need to decide whether they want to cater to the existing collector/hobbyist or target new people and try to expand the hobby.

For the existing collector, somewhere regional e.g Albury would be worth considering.  Venue hire would be cheaper, there is ample accomodation around town, direct flights into Albury from Sydney and Melbourne with either REX, Qantas or Virgin Blue and it is roughly half way by road between Sydney and Melbourne.  Somewhere like the Kinross Woolshed for example would be ideal.  They hold major concerts there so power would not be an issue, the have food and grog and plenty of room.  Attendees can make a weekend of it like many car clubs do that hold meets in and around Albury.

If you want to try to reach out to as many people as possible then it has to be in a capital city, preferrably Melbourne to try to encourage the various parts suppliers and retailers to attend.  They won't attend if it is too far away.  It is simply not worth their time to rent a truck, load it up, travel to the venue and cart it all back again.  As has been said, the organiser/s MUST be impartial and offer the same options to each and every retailer.  No restrictions on what they can and can't sell at the venue as was the case in '09.  Easiest way would be to charge them by the square metre for floor space.  Although AMD is not in Melbourne, they do have distributor/s that can fly the flag on their behalf I'm sure.

A way to possibly raise funds to hold the event as opposed to holding an auction may be to raffle a machine or two??????

Anything is possible with some $$$ behind you but more importantly the passion, co-operation and understanding that you simply won't be able to please every person no matter what you do and how hard you try.  Anyone that has a crack at doing something like this should be applauded and assisted in any way possible.