All right everyone, I'm 99% sure this submod works just fine! I just played 200 turns of a Normal Campaign with the Realism submod as Rome and let me tell you, the AI is playing just great! They have been recruiting just as normally as they have been in vanilla DeI. They have multiple full stack armies with a mixture of various units ranging from light to super heavy units, just like in vanilla. They play just as aggressively as they do on normal difficulties. In addition, they still build multiple 20-stack fleets that have diverse units (and one light ship takes 4 turns to recruit). The campaign I was playing on developed into a great game just like in vanilla. The AI took territory from each other and expanded into small empires, formed alliances, and was not afraid to go to war with the player. At this point in the campaign, the whole world was divided into 2 super alliances and it was really getting interesting. And all reforms had been discovered I believe (except I was stuck in Polybian because my imperium still wasn't high enough).
Ultimately, I don't know what people had been saying about the AI not working with mods like these. Perhaps in the past it was indeed fishy, but there could've been other parameters involved too. Suffice to say, it works now for both the player and the AI and the latter performs normally. Maybe there is something I am not noticing but I can be confident and say that the AI works just fine. If you do try it out for yourself, please let me know your experience!
P.S. I took about 30 screenshots from this latest campaign to showcase how the AI turned out after 200 turns. Unfortunately, I could only post about 10 because of the upload limit.
P.S.S. I'm going to fine tune the submods and change some recruitment times for some units. (I disliked having 2 turns for levy troops because they were classified as medium troops).