The post Septem dynasty legionary reforms seems to have been heavily based on the Marian reforms. Looking at the ending of the Legionary quest-line it's pretty clear that the generals now provide for the welfare of its men out of their own pocket, just as the Marian reforms had ushered in, and the changes in equipment toward a more standardized force with Axulian (spelling?) units seems to be further evidence of such inspiration. Given the success they have had in sowing unrest in the fair-weather friends of the Empire, wouldn't this be symbolic of the transition from Republic to Empire, and the Agustin/Marian reforms after decay had set in after disastrous wars? Obviously the Empire is already an Empire, but many changes beyond a more dynastic rule was the result of the change.

If I recall correctly, the Legion of Morrowind was pretty much identical to the Legion of Skyrim in terms of equipment, though they had different rank system. It was Oblivion that made the exception here.

The Legion of Skyrim is perhaps better related to Late Imperial era, talking about Rome in 4th and 5th centuries. The situation after Oblivion crisis is an obvious allegory to the Military Anarchy of the 2nd century, with Titus Mede, a petty warlord, capturing the throne and leading his empire by sword. Provinces are abandoned due to lack of resources (compare Britain to Hammerfell), the Legion is less restrictive in its requirements (compare to Foederati) and the Legion seems to be divided into elite troops protecting Cyrodiil (compare to Comintanteses) and lesser, local troops tasked with less important provinces (compare to Limitanei).

If the Legion of Skyrim was more about Marian era, it would for one be much more competent and actually capable of holding the Empire together, instead of struggling to keep even some petty Nord peasants in line. Generals paying troops from their own pockets is something that was the norm for centuries and not just in Rome.

But I do not see any comparison to the Auxilia in Skyrim's Legion, I must say. They would be closer to the Limitanei/Comitanteses in my opinion.