I was having a thought about Dastan being a cohort gained via the leadership feat, and the primary character being "the keeper of 'the sands of time'." A buffing sorceress would do the trick. Of course this wouldn't kick in until level 7 in Pathfinder. So until that time, play as the princess and buff the paladin (you are not the chosen one, but I buff you anyway!).
This accomplishes the original character goal, and the primary character will be on par with the rest of the group. Of course the DM is under no obligation to let you make or play your cohort, so be sure he is cool with that. Explain that your main character will be the cohort buffed by the sorceress. Use the builds suggested earlier for the cohort.
Or do the opposite. Play as Dastan until level 7, and then get a Sorceress Cohort. I would not suggest this however, because it introduces MAD and Feat Tax to Dastan, whereas the Princess already has an Uber Charisma and can afford the feat.
Not a big fan of oracle btw. The new classes from Pathfinder are a step in the wrong direction....gunslinger