Gallo-Romans Composition with auxiliary tribal troops from Western Europe.   Very powerful Romanized troops scattered in Cologne. Heavy barbarian cavalry of Alamanni and Franks. I know it only lasted less than Palmyra.    I like the concept, plus Dominate troops are starting to appear.

I drew a lot of inspiration from thinking about Nero's colossus.  

Very interesting, I thought about that but I must be careful. I thought a lot about Christian iconography. I have some examples of Roman painting and late painting. Mostly to add effects on top of the drawing. There is a statue of Constantine.

Hard to know without having more information, many deities would look like this. For example, this is apparently Jesus (Christus-Apollo according to a couple of flimsy sources), from the 11th century, with his right hand raised commonly associated to a blessing: There the orb again seems a sky symbol. I'd be tempted to say the eight arms are all the "sabbats" (related to the seasons, which appear on the four corners of that picture), but it's the Wiccans that in modern times put together the partial sabbats different ancients would observe. Still, you can check da Vinci's Salvator Mundi painting, where the crystal orb is taken as the "celestial sphere of the heavens": All this just to show more modern and analysed stuff, and that there could be a continuity in interpretations. After all, the sphere you drew reminded me of the Farnese Atlas sculpture, from the 2nd century, which has the ecliptic among constellations basically where you drew it (in the upper right, apparently by chance? Because the new picture you are posting is not that clear on that):   Regarding emperors holding it, the 2026 Encyclopædia Britannica (https://www.britannica.com/art/orb-royal-emblem) states it's a "symbol of the cosmos, or of the universe as a harmonious whole, is derived from the ancient Romans, who associated it with Jupiter and, hence, with the emperor as his earthly representative". I've just found some people online claiming it's the world, but without presenting too much evidence. For all practical purposes, it represents everything, and the dominion over it from the one holding it.

Imperator of Rome is a very good, very immersive game, and its Paradox community has some great ideas.