I will say that I have never seen any circumstances where any US carrier could dispatch a flight to any airport forecast below landing minimums unless they used 3585, but as you say that was for domestic only. For flag, they need the minimums. It doesn't matter if the alternate is good, (it would have to be above alternate minimums, say 400-1 or higher) if the destination is forecast to be below landing minimums, then it is illegal.
Those minimums need to consider the aircraft, the pilot and the facility(airport, runway) minimums, and the highest of the 3 determines the legal minimums.
The only possible way around this is to dispatch the flight to an intermediate point which would have legal minimums and, if, at the time the flight reached the intermediate point, and the weather has improved at the destination to where it does have minumums, then the flight could be dispatched to the destination.