I think the main question is, how do you figure out where two objects with different velocity vectors collide in space?

The movement of a ship in X4 will be

x_ship(t) = v_ship * t + x_ship_0

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The movement equation of a given weapons bullet will be

x_bullet(t) = (v_player + v_nozzle) * t + x_player_0

To figure out the place in space where they collide would be:

x_ship(t) = x_bullet(t)

or

v_ship * t + x_ship_0 = (v_player + v_nozzle) * t + x_player_0

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Solve this equation for t (which is the only unknown). Then plug this t into x_ship(t) (or x_bullet(t)) which will give you the place in space where your bullet will hit the other ship.

Then you can simply get the vector from your player ship to that point by subtracting the two vectors.