I would suggest to notify the buyer who clicks on the Buy It Now with "Your bid/offer has been sent. You will get notified when the buyer accepts or rejects your offer".
And on the buyer side, he has the option to pick which offer to accept, and when it's accepted, other offers will get auto reject and the notification will be sent to the rejected bidders.
By doing this, the seller still have the time to properly check who are the genuine buyers, eg: checking their feedbacks/comments etc. Rather than honouring the sale on a first come first serve basis. It doesn't work like this because this is not eBay where you can file disputes if a buyer did not complete their deal.
Just a thought!
Don't really like the way it is right now where we'll get id**ts purposely clicking the buy it now and not completing the transaction, and we'll have to ban them personally.
Hope you can consider!