Gothmog said:
It seems the big one gives you prestige as well...this means that it henceforth will be a game breaker.
Erhhmm. In any non-world-conquest game, just HOW many provinces in which you can build Grand Shipyards are you likely to own in your personal demesne?
You are likely to get more prestige from War Academies as they can be built in any province with a high enough income, and even then, to get a truly momentous prestige boost you need a huge rich demesne. Those +1 prestige and piety are per year.
If you own ten very rich provinces, each with a Grand Shipyard, a War Academy, a Theatre, and a Grand Palace (a very interesting disjoint demesne is needed for this

) - that is still only 40 prestige extra per year. Certainly worth getting, but game breaking?
The main point is that prestige and piety in CK used to be a declining function over time in CK unless you kept constantly expanding, since you would be using up all the "bonus upon being built" bonuses. Now, you will stilly be getting those bonuses in the early game, but if you build up your realm, you will still be able to act in the end-game.