Wasn't the Garlond Ironworks super hopeful they'd figure out some time traveling tech during 5.4 before the machines got overworked? Maybe I'm just misremembering.

I not so secretly had dreamed Diadem 5.0 would involve time-traveling to 5 years ago as a form of delivering a "XIV classic" without the real damage a real classic server would make. But in terms of plot that would be pretty pointless.