Moby, I think you missed the point - you want to have the sale proceeds in your account BEFORE the purchaser has paid for the shares you have sold. The purchaser's money is drawn from their account the same day you receive it in your account, therefore you are not foregoing interest. The three day settlement period is there to enable all the legalities to be performed and enable the ASX to perform a review in the event of any suspicious trading patterns.
If you are running two accounts which means you have to wait for sales to settle before you can enter into a purchase contract (although I still fail to see the problem - I have two separate trading accounts and I'm still able to sell in one, and buy in the other at the same time - or does your broker require you to have the funds in your account at the time of execution?) that is your fault, not the fault of the trading system under which everyone operates.
If you sell a property which has a settlement period of 6 weeks, do you expect to have all the sale proceeds in your account earning interest (or available for you to use for whatever you want) from the date you exchange contracts? Unless you're an idiot you wouldn't - the same applies to a contract for the sale of shares.
