Dude, Willa Holland aka Caitlin Cooper is too young. She's only sixteen years old. She was only 14 when she signed on to be in the third season, but was made a series regular when the decision to kill of Mischa Barton was finalized. Even in the show, she's only 15.
If somebody wants to do a new OC story, why not have those two MILFS, Kirsten and Julie tickled. Let's not forget that they are rich and could make good hostages for quick rich schemes. Well Kirsten is anyway...