Quantas ... I agree that airflow is an important consideration - but do you know, for fact, that this was the primary design factor for the engine tilt, or are you speculating?
Here are a few observations .....
1) The 727 and L1011 do not appear to have angled inlets. The 727, however, has upward sloping #1 and #3 engines, which increase downward moment.
2) Using the horizontal stab trim adds drag - an aircraft is designed to be inherently balanced for cruise configuration with the stab in an optimum (low-drag) position.
3) the downward moment is the vertical component (which I agree is relatively small) multiplied by
the radius arm from the cg - which is large. This may be just enough moment to enable the horizontal stab to be optimized for cruise.