I like this idea. I always found it a little weird having my ships being built and then suddenly appearing out of the shipyard when finished.
I agree with Yottsu's point of view, that it should be part of the construction time. So if it took one second for the ship to steer itself out of the shipyard, then take away one second of construction time that it would otherwise spend building and make the moving out of the hangar second of movement part of the construction time.