So, to me, Lance is the perfect Baby. And that's without even taking into account that Baby was played by Jennifer Grey (nose job!!). But Lance. I can just picture him wanting into this dirty dancing world, but he's awkward and can't dance and he never knows quite the way to do things, so he ends up telling people he carried a watermelon. He, like everyone, is in love with JC (Johnny Castle - JC = JC! Also, Patrick Swayze wrote the classic "she's like the wind" which is totally a song JC could have written) the gorgeous dance instructor. And can JC ever move! He dances with his sassy partner Justin, and they're totally the golden couple, but Justin gets pregnant (not by JC, he'd never do that!) and needs to get an abortion, because lord knows how they delivered mpregs in the 60s. So in comes Lance to learn how to dance and fall in love with JC. And yadda yadda yadda, after some awesome scenes of JC and Justin teaching Lance to dance, and then JC and Lance in the water practicing thier lifts, it all culminates with "Nobody puts Lance in a corner!" and a perfect jump from Lance into the arms of his lover JC. They will have had the time of their lives.
As for the other nsyncers, perhaps you'd like to sort them out with the other characters. I personally like the idea of Joey as Baby's sister, just for the talent show performance. Or perhaps you have a different casting entirely. Or perhaps you haven't seen Dirty Dancing (wtf?).
Also, I thought I'd throw out a challenge for someone to popcast Desperate Housewives. I've never seen the show, but it seems to me it would be ripe for popslash, what with there being 5 housewives. Bonus points if JC is not Eva Longoria's character. ;) If you're a fan and you've got some ideas, post away!