What about Jason? Couldn't he be the storm? Percy fails in his big decision and becomes Gaea's prisoner, so it's up to either Jason or Leo to save the day and defeat Gaea.
See it all depends on what the "world" is referring to. If it means Gaea, then yeah I could see Jason being the storm instead of Percy. Leo and he could team up and be awesome baddy best friends and fight against Percy and Gaea and wow that would actually be a really freaking cool battle.
The only slight problem I have is that I don't know if Jason, or his dad Jupiter, are storm-makers necessarily...Has Jason ever made a storm on his own before? All that I can recall is him blasting with lightning, never causing wind or rain or anything like that. Percy has proven that he is a storm-maker with his ability to generate hurricanes, and his dad Poseidon holds the offical title of storm-bringer, as it says in The Lightning Thief when Percy is first claimed.
But again, I think it all comes down to what the world is in this sense, Gaea or loved ones and places?