Being able to place buy order to auctions could help the economy. To find the real price of stuff. The sweet spot between bids and offers. Economy is very important part of game and will become even more if/when vendors will fade.
Today some offers are way high even that there is alot of them. longer times can help somewhat perhaps.
Buyer will pay the auction fees, of course, so there is clear gap between bid and offer queues.
What do you think?
Edit: the example, how I imagine it working:
1) I place the bid for 4000 cherries for 5c each on auction
2) I pay all the sum + auction fee in advance (say 24000c)
3) anyone can sell any amount of cherries to auction house for immediate currants
4) auctioneer store the stuff, send a frog package when whole bid is complete
5) I can cancel the the bid anytime, receiving already stored stuff and remaining currants except the fee.