Roman regiments of the VIth century.

[Zames]

I wasn't implying that the Valentiniani continued to exist. I just saw Felices and am used to seeing that term.

Probably I badly explained myself, sorry, I didn't mean you were implying the later existence of Valentiniani. But now I'm curious about "felix" and "felices", I wanted to know why these terms were used to name specific regiments.

Anyways, I am interested in the appearance of the 6th century army. What would have a standard professional heavy infantryman looked like? I don't know much about the era, outside historical accuracy mods for RTW.

That's not sure, we unfortunately lack reliable iconographical sources (apart from the plate of Isola Rizza, which shows a probably romano-byzantine heavy horseman) and the two manuals we have (Peri Strategikes by an anonymous and Strategikon by Emperor Maurice) could be a useful source but we should consider the content as something the authors wanted to see on the battlefield, not necessarily what they saw.
The more widespread helmet of the period, according to archaeological finds, was the Spangenhelm-Baldenheim in its variants (4-6 spangen, chainmail neck guard), recently divided in romano-byzantine productions and later germanic productions. This kind of helmet was adorned at the top with feathers or horsehair crest. It's also a possibility that they had, as alternative, a lamellar helmet like the "typical" Longobard helmet. Even if in many moderns pictures we see them, ridge helmets weren't used.
At least first and last lines of the regiment on the battlefield should were a chainmail, but we don't know its dimensions. Maurice doesn't mention it, but the Anonymous recommends to were a himation under the chainmail, a padded jacket. We don't know if it was really worn. Also scale armors and lamellar armors were used, but I don't think an infantryman could afford them.
Shields were of oval or round shape, their dimension was probably the same of the ones from Dura Europos.
Heavy infantry was armed also with spears (akontia, the contòs was the heavy cavalry spear ), but they probably were more similar to javelins: Maurice infact recommend to the men of the first lines to throw their spears as soon as possible and to use swords.
Swords. This is a great problem to me. In Peri Strategikes they were not mentioned, in the Strategikon infantry should have the "sword used by the Heruli", but unfortunately we don't know which kind oh sword these germanic people used. A possibility is that they used a kind of scramasax (which, according to my latest readings, such as articles of M. Kazanski, could be a weapon of eastern origin), rest of which were found in the castrum of S.Antonino in western Ligury. Talking about spathae, the more widespread type of the period was the Type 4 classified by E. Oakeshott.
Last, but not least, heavy infantrymen were armed also with plumbatae/martiobarbuli.