There is a way in Ebay to list a Buy It Now price on an item that is also under auction, and if someone clicks that button to pay the Buy It Now price it garners the item at that time. I have no idea if Ebay will allow an auction to be revised like that, or ended early and re-launched with a Buy It Now price.
Correct on BIN option. and an auction can be modified if there are no bids, IIRC.