Jabber, I think you may have something there.
Only problem I see is Bidder #2 may not answer your offer, since they are not obligated to buy. How long do you wait for him/her to reply. I suspect many that use eBay don't even know what a second chance offer is, and may think you are trying to pull a fast one.
I've never actually tried this myself, so don't really know. I hope you get more input. If you try it, let us know how it works.