Originally Posted by Reality_Czech

Wouldn't work with this specific example. There are a few taxes that are collected even with transit in SIN on the same plane. These would have to be refunded (or collected) if you alternate between DXB/SIN transit point.

BA and QF YQ may also differ which would require potential reissue.

edit.

In saying that, I don't think $125 charge would apply under the spirit of the OWE rules. However, it will still require reissuance by the airline.