Sabo, I don't think that getting the Great Library and not having contact with anyone is such a bad thing. Once we do establish contact, we'll IMMEDIATELY catch up to every known technology! This only INCREASES the value of the Great Library. The Great Lighthouse is not a bad wonder at all, but it doesn't guarantee anything. We have so much ocean between us and other continent that most of our galleys will sink, anyway.
We could build the Great Library, build temples and libraries in every town, and concentrating on building up culture and money while other civs are researching everything for us and warring with each other. When we do meet them, we'll have nice culture and a spotless reputation. We could go for a cultural win, diplomacy, or even use our island fortress as a staging point for a massive invasion.
I don't see any problems with the Great Library at all. The only issue I have is with Philosophy. It's a required tech, and someone WILL get it before we do, netting us a big bagel, zilch, nada...