If I remember correctly, the idea was to use Paige as a Paul Heyman girl, but that idea fell through because they wanted to use Paige as a face, and bring her to the main roster to feud with AJ once the AJ vs. Total Divas storyline is over.
If I were WWE, however, I'd take a long, hard look at the division, and bring Paige up now. Sure, the rumored Natalya vs. AJ feud should work, as both can handle themselves in the ring and on the mic. But if you want to establish Paige as a challenger, bring her up now and let the WWE audience get 'hot' for her in the same way the NXT crowd has.
In many ways, she's the most over wrestler there, and for good reason. She's a great wrestler already, and I don't throw around great lightly. She knows how to work the crowd, her ring psychology is superb, and her in-ring work needs no more fine tuning. She's ready now. Get the audience used to her, and give her time to get acclimated again to the road. It shouldn't take long, with her mother being Saraya Knight and all, a woman who Paige traveled with and worked alongside for years in England and other parts of the world.
Which is why I never understood, for goodness sakes, why they encorporated that silly 21 years rule with her. If she has that much experience on the road already, I think she can handle it in the WWE. There's no part of her that needs improvement in the wrestling department, so have her drop the NXT Women's Title, bring her up here, and get her established.
If there's ever a chance to bring back to life a dying division, it could be Paige and AJ, playing the roles of Trish and Lita, or Trish and Mickie. The sooner, the better.