If Castaway was not romantic enough for you (and, really, how could it be? Tom Hanks never really loved that volleyball) and Lifetime’s take on The Blue Lagoon is too been-there, done-that for your tastes, MGM and Temple Hill Productions just might have something to rattle your palm tree. The studio has optioned the rights to Tracey Garvis Graves’ “On the Island,” a desert island-set romance with a big twist. Instead of just tossing a pair of mismatched lovers into the sea, Garvis Graves has upped her characters’ differences by age (older woman, younger man) and also thrown in a medical complication (one of them is recovering from cancer) to make the drama even more, well, dramatic.