>>211786997 (OP)They would see some similarities but in the end Byzantium is a foreign place to 1-2nd century Rome. If Diocletian saw the 7th century he would probably recognise most of what was going on but if he saw the 9th he wouldn't see much outside of law and the Imperial court ceremony as familiar since Diocletian is the earliest Emperor they have these things from.
>>211787128Appian writing in the 140-150's calls Rome a monarchy without any reservations, with Augustus as the first. They were over the totally-not-a-monarchy phase of Augustus, even in 69AD there were calls for the restoration of the Republic after the death of Nero. They had a pretty clear sense that the Roman Emperor was a monarch.