The ATM solution would be the worst due to the bt200 transaction fee plus a fiver or so UK bank charge and a maximum bt20-30k per transaction.
Bring in the equivalent of USD10k cash for starters get set up with a Thai bank account and go with wire transactions there on.
But they need to comply with IATA regulations to maintain their ability to fly on international routes and an IATA inspector or even local regulatory authority can carry out an inspection at an international airport and ground an aircraft if it fails to meet international requirements - even a sanctioned nation would want to avoid that
Wouldn’t ya know even the Head of the NTSB is female - Jennifer Homendy, but from her Wikipedia page seems she has had no actual experience in ATC or any other aspect of aviation but a lot of previous involvement in labor unionism.
If the crew didn’t complete the journey the number of take offs to landings would not be equal which is not good.
Depending at what point in the flight the engine fails the airline’s default policy is usually to return to home base due to the logistics of trying to replace an engine at an outstation or diversion airport - either way the safety of the aircraft is paramount.