As I read it any cards played as hired ships stay as hired ships till the end of the encounter (the rest of the Planing phase, Reveal phase and Resolution phase), so this means they can not be taken from you as compensation right?
In essence you could protect your entire hand and be immune to compensation if you make your entire hand hired ships. (obviously losing the encounter would lose them all though).
This is correct. Of course, since your opponent knows that he won't get much in compensation, he's more likely to play a strong card, which makes it more likely that he'll win and that you'll lose all those lovely cards you hired out...