Here is one of mine:
I think the eggs in the derelict, the derelict itself, and the jockey are all part of each other. The derelict ship is actually the last phase in the xenomorph life cycle. When they've conquered an entire planet, and its one big hive, part of the hive grows into a derelict (eggs included). It would break off, and fly to a random planet (inhabited or not), thus spreading the seed.
The "ships" aren't always wish-bone shaped, like the one on Acheron. The shape doesn't matter.
How theses things can fly, I have one idea, but its a stretch. There was this one forum member (forget who) who was talking a while ago about how maybe the aliens can manipulate dark matter, letting them "float" for small distances, explaining their incomprehensible agility. (Scaling walls, ceilings, ect.) If individual aliens can float for small distances, the a derelict could soar. Maybe that's how. I really just don't know.
And the Jockie, again doesn't really fit in with the theory but I'll think of something.
Another point: If the jockie and derelict are one and the same, it makes sense for the Jalien to be friggin monstorous like it is in that one pic. (You know, that scene that never got filmed with Lamert and Kane and Ash walking beneath it?)
I got couple more, I'll post 'em later. Every ones bitchin at me to get off the comp.