A little confused by the post (is it divas becoming the world tag champs or is it a new diva's tag division with belts).
Either way it would be an awful idea.
First off, there are way too many divas in the WWE, what they need to do is weed out some of the diva's as they are nothing more than eye candy and bring absolutely nothing to the table (Tiffany, The Bella Twins, Kelly Kelly (no thats not a typo)). Trish and Lita brought something to the table (fans of both by the way), Natalya, Beth Phoenix, Gail Kim and even Melina bring something to the table, but most divas are as useless as an asshole on an elbow (if i want eye candy, there is this thing called Maxim Magazine and Porno). For a diva tag division to work there would have to be enough diva's that can put on a decent match, and even with that it probably wouldn't work (didn't work in the 80's).
Secondly, if there were ever a diva team that could actually challenge the world tag champs (like if bull nakano and awesome kong were a team) it would be OK (kind of like when Chyna was IC champ), but most likely it would never work and if it did it would be a 1 time only deal.