What if he actually did? When he went out with Rachel, Annabeth got really steamed, right? And she called him a coward once, in The Last Olympian. Doesn't she deserve it? The point is, what if Percy married Rachel or Thalia, even though Thalia is a Hunter and Rachel is the Oracle? Imagine if Percy dated somebody like Clarisse La Rue or Piper McLean or something. What do you think?
Also, since Luke was the hero of the PJO Great Prophecy, what can Percy do? He's one of the most famous heroes. He helped find Zeus's master bolt and Hades's helm of darkness in the first book, he was found out to be the only child of the Big Three since Thalia became a pine and Nico and Bianca were frozen in time, he rescued Grover from the Polyphemus's cave and saved Thalia Grace, he went on a quest to stop Atlas and rescue Artemis, he went into the Labyrinth to find Daedalus and stop Kronos from rising to power, and at last he saved the day during the Battle of Manhattan by giving Luke back the knife he gave Annabeth to kill himself...and stop Kronos. Then, in the HoO, he was one of the Seven. Luke wasn't much important. Although he was the hero of the prophecy, everybody thinks it's Percy. And he gets the offer of immortality. Why doesn't anybody remember Luke Castellan? I was thinking, if Annabeth agreed to like Luke and betrayed Percy, accepting the offer of joining Kronos's army, then what would happen?