It probably wouldn't solve all the issues with pvp, but gc said that it would take same amount of work to create a 4th spec for every class and to create a new class. So I think these are all great ideas and I would love it if these were to get implemented. This would also give them the opportunity to homogenize classes as a whole instead of just specs.
btw.. I hate the idea of another dps priest spec I would love it if they implemented a melee healer like disc was supposed to be instead of creating a new dps spec for priests.