If the Losties do reset time we know there will be a bunch of problems with the time/space continuum, thus the title LA X, the space probably meaning something went horrible wrong. Here is one of the things that might happen:
If the hatch is never built they might never put the numbers on the radio tower. Leonard would never have heard it and never told Hurley in the mental institute. Hurley would have never played them in the lottery and never would have one. Now, the bad luck still would have happened, but he wouldn't have gone to Australia to talk to Leonard's wife about the numbers. That means he would have never been on the plane and therefore never on the island.
Whatever he affected on the island would be changed. He would have never done a census and they would have never learned that Ethan was not one of them.
A number of things could happen now that Ethan is still undercover.
He could have killed them and taken the children. He could have kept doing tests on Claire. He would be alive. Etc...
Hurley would have never found the Dharma van and ran over some Others in the Season 3 Finale. That means:
Swayer, Juliet, Sayid, Bernard, and Jin could all be dead or captured.
Hurley would have never been in 1977, Radzinsky would have never asked: "Who the hell is Hugo Reyes?" and Phil would have never answered: "He's the fat guy."
And of course the biggest thing:
Hurley would have never been on the Helicopter and therefore Sawyer could have been an Oceanic 6.
His mom would have never known what happened.
Sayid would have never killed the person outside his mental institute.
Jacob would have never given him the guitar.
He would have never bought all those seats on Ajira 316 and therefore all those people would have crashed too.
Without him they might have never returned, because it wasn't correct enough.
So, by doing this reset they could have made there lives actually worse than better.
Any other big Hurley moments that could be changed now?