Personally, I'd like the "mysteries" of the original films to remain that way. We don't know for certain why the Nostromo was rerouted, but it's fun to speculate. We don't know the story behind the space jockey and the derelict on LV-426, but it makes for interesting conversation. Another prequel film telling us IT WAS ALL DAVID wouldn't be my cup of tea. Don't get me wrong, I like the character and Fassbender was superb in the role. But I'd rather not have David's shadow loom over the original films. Does the character deserve a conclusion? Yes. But just don't tie it into the events in Alien.