The purpose of the Late Roman Draco standard.

[Robert Vermaat]

Moved from the thread about auxiliary standards:

Whithout appearing to be overflating my ego, I believe I am the only person to have made this connection, and I am astonished that no historian, including Matthews, has examined this matter as I believe it really merits further investigation. It may well be that as the Roman state became 'Christianised' that another means had to be found to represent the Emperor, as human representation such as imagio's may have fallen out of favour as they may have been reserved soley to represent Christ himself.

Maybe others who thought of it found too little evidence to make a case for it? Just speculating of course.
Your ideas about Chritianization I must rject, because the representation of the imperial family continues throughout the 4th and 5th century - there's no evidence that this became reserved for Christ only. We find the images of emperors on shields and banners I think, so there would be no reason that this was dropped during the period we're discussing.

Just because no source confirms what I have stated does not disprove it, only that perhaps the sources are there but no historian has bothered to make the link.

Well, that's not how I like to discuss evidence. Just because there's no source confirming something, usually means there's no way to confirm it. If you still want to maintain something without proper evidence from any source, you're on purely speculative ground. If there are indeed sources out there, but yet unmentioned (which is of course possible), I'd suggest you find them, but in the meantime admit that there is not enough evidence.