Assuming a seized N1 (or perhaps even just windmilling), will the turbulent air spilling off the engine affect lift, especially at high AoA?
That particular aspect is designed for. If you look at the inboard side of most high-bypass engine inlets, you'll see a large strake (we sometimes call that the 'engine ear'
) I don't recall off hand if said strake is used on the 747-400, but its on the same engines on the 767 (and is definitely on the 747-8). It's purpose is to energize the spillage airflow from a shutdown engine during low speed/high angle of attack conditions so that there isn't airflow separation over that area of the wing during approach/landing conditions.