The purpose of the Late Roman Draco standard.

[Robert Vermaat]

I'm not implying that the Eagles represented the Emperor, I've read in a number of books that the Eagles represented the might of the Legiones, were in fact the physical representation of the Legione.

OK, fair enough. But in order to introduce a standard representing the Emperor, you'd first have to establish that anything like that was indeed present. As I've shown with the purple colour of the Persian standard earlier, the colour of the draco tail is not necessarily leading to an identification of the standard with the emperor by definition.

It would have been a good way of indicating on the battlefield which units were legiones and which were auxilia, something that during the Late Empire period may have been something of some importance as some historians claim the arms and equipment of the Legiones and Auxilia were the the same at that time.

Well, auxilia were not the same as the 'old' auxilia anymore. Late Roman auxilia were new, elite, regiments newly raised. Therefore I would see very little sense in any reason why it should have been necessary to indicate on the battlefield which unit was a legion and which an auxilia? Such differences were gone by the 4th century. There were old-style legions and new-style legions, as well as auxilia, scholae and other types of units.

What symbols were used to denote the presence of the Emperor or to depict him if he were not present.

That's a good question. I'd like to hear more about that myself.