Naruto would need to be able to use Fire Style to pull off a Clone Explosion Jutsu. As for the Crows, Naruto can already use the tranformation technique. The only reason he doesn't use it often is because he lacks the subtlety to do so. The last time he did it, he turned about 200 clones into rubble during the Pain battle.
I do believe that the exploding clone is simply a fire-style shadow clone, similar to Kakashi's lightning style one. I'd love to see a wind-style shadow clone from Naruto. As for transformation being used, I do believe that Naruto is subtle enough. He uses it when needed. Also, transformed clones are not what the OP was talking about. Frog clones would be weird, if you ask me.
Is fire element necessary for exploding the clone ? I don't think so I think it is a different jutsu not attached to any element.
Itachi's exploding clones were mainly the reason Itachi was paired with Kisame and his exploding sharks. Itachi is a well known fire style user. Also:You must be registered for see linksshows that even though it isn't labled as a fire style technique, Itachi is the only one to have used it. Kind of like Kakashi's Lightning style Shadow clone against Pain.
Then Naruto should develop his wind style clones....