You don't want to do a BTCpay right before the order match is set to expire (especially in the future, when blocks are closer to being full).
Can this be foolproofed somehow before going mainstream? I'd hate to think of all the posts on the forums when people start losing BTC. Maybe the BTCpay operation can accept an order match number as an optional parameter and the escrow time extended if necessary for the amount of that specific order only, provided BTCpay is called before the offer expires. The number of blocks to extend would be based on what the protocol determines is reasonable at the time or could be hardcoded initially.
I think maybe there is some confusion here?
There are two different Expiration Scenarios. 1) The expiration of the unfilled order (order-expiration). 2) The expiration of the time period a buyer has to send bitcoins to the seller through BTCPay (order-match-expiration).
From what I understand PhantomPhreak is talking about order-match-expiration. For example, an order is matched and the buyer has to push a BTCPay transaction to the blockchain within 5 blocks. He pushes it before 5 blocks are finished but it takes longer than that for his transaction to be confirmed. He loses his bitcoins in this scenario.
In terms of order-expiration, that should never cause you to lose bitcoins. When the order is matched, the order is no longer unfilled and therefore the order-expiration is no longer relevant.
Please correct me if I'm wrong.
You are correct, I believe.