...just an idea...
Supposing a ship you have your eye on is particularly rare, and particularly powerful (maybe). Rather than being mass-produced, you see, it is handcrafted, and takes a while to build after you make your purchase up front. After a set amount of time, the ship becomes ready, and you can go and pick it up at the planet you ordered it at.
I haven't given it a try yet, but thinking it over, I believe it could be possible with the current engine, provided it is all set up with missions instead of from a shipyard. 'Cause there's no way to make it so a shipyard purchase doesn't actually change your ship, right? Yes? 'Cause if there is, that would be cool.
Or, is there a way to trigger a cron or an NCB just by going to the shipyard of a particular planet, but not buying anything (i.e. the shipwright notices you snub the other options, but can easily afford them all, and so makes his sales pitch thus)?
These things could be looked up in the bible, but I had an inexplicable desire to share the idea. Perhaps it's even been done before, I don't know.