Sounds great. The last think we need is feature creep that doesn't actually add anything to game-play.
What I would suggest is adding in a "captain cabin". Either in 2D or 3D (if there's enough time) to allow the player to look at charts, review "news" check known prices of goods, see his reputation level, or his progress in "navel exams". Hell, this could double up as a menu screen I guess. Kinda like the bunker menu in Metro 2033.
Hmm... I see where you're coming from, concerned about exploitation. However I really like the "cinematic" feel that a 3rd person cam offers. I's good fun to see that damage to your ship after a battle. Like Batman in Arkahm Asylum a scared and battered ship is almost a character itself.
I'd go perhaps a midge further that your suggestion and say no more that +- 50% higher than the top of your mast.