I don’t know either, but this is a great idea if it can be implemented without compromising other aspects of the network.
It feels like this idea is the guitar solo for the Bisq-like DEX idea discussed here: A bisq-like dex to trade ERG for fiat or BTC and other cryptcurrencies - #3 by kushti
By making the transaction contingent upon some kind of handshake, you could remove a huge amount of anxiety.