So, I've seen it said on this community that the possibility of a centralised Holy Roman Empire existed well into the reign of Charles VI, and that it only really stopped during and after the War of Austrian Succession? I've seen others argue that the Thirty Years War was the nail in the coffin for a centralised empire.
So, my question is this, how does one get a centralised empire, when would be the latest date for it to be achieved and how what would the consequences be? Would such an empire be sustainable into the 20th and 21st centuries?