Yeah, I've got to agree with Gary on that. First in, first served. As a buyer I've been on the losing end of that sort of scenario - nothing to be done about it, the person who hit the buy now is the new owner.

I had a package from Aramex do the same thing. The tracking said the package had been delivered, but there was no sign of it. I waited a couple of days and then it appeared. Don't know if they just delivered it to the wrong address, whose residents then dropped it off, or if they are playing games with the tracking and marking them off as delivered before they actually do it. That's a very impatient and unreasonable user you have there though.

Will it be possible to make listings that are cash only for in person trades? Or will PING be added to these by default as well?

Unfortunately there are some extremely strange people on Trademe who do list with a requirement for contact and/or payment within 2-3 hours of the close of the auction. The ones I've seen have put that requirement in the auction description (usually at the bottom, sometimes buried under quite a bit of other text). Personally, I thought it sounded silly and carefully avoided having anything to do with such unreasonable people. Like the OP, I'm not always in a position to respond immediately if I win an auction during the day (say with autobid). Rather ammusingly in one case I saw, an auction...

Anyone know what happens if several people have that Auto bid function set up in Bid bud for a particular auction?

If you don't want to pay the withdrawal fee, you could just edit it to something else. Or delete most of the content, make the price astronomical, shorten the run time and add something in the description discouraging anyone from bidding on it.