Worst, Rome would change weapons, but not armors, and tactics.
Basically, any "Future" RE army would look like this:
Even RON, that allowed a Super Roman Empire, managed to change the soldiers look of Rome in all ages.
I think i find another way to divided the RE in three parts: make Rome conquer Persia. Considering this video:
If Caesar managed to conquer the Parthians, then, later in history, the sheer size of that empire would make that the emperors decided to divide the empire to managed better. Maybe the...
But how long would the triempire resist before the inevtibale collapse? If i understand the situation correctly, the western side would be the first that will fall, making the central and eastern side surviving a little longer until they fall, too.
If they fall later than OTL, How that would...
Could work, specially if Diocletian created a solid way of replace the emperor and the princeps (because the empire would be reunited again by one).
It would be interesting if we take the "worse third century crisis", "the Triarchy", and the "Theodosius had three sons" and mix it to create a TL...
For some reasons, the UK is the first to discover America, and sent settlers and soldiers to south and central America t, while the spanish had to conform in colonizing north America.
Uf, TTL WRE is going to fall earlier than OTL WRE, with Goths, Huns, and Vandals attacking it. I'm envisioning that the two other REs would pay the Barbarians to attack the western side while they just sit there.
Ok, that's an interesting take, and could butterfly the Vandals and Islam (this last is in doubt), but the question is. Could this division accelerate the fall of the Western and Eastern Empires, or could that division delaye their fall?
No Colombus, to start, then, we can think that the other European powers would be bussy screwing Portugal that they wouldn't launch an expeditionary expedition to "search for another rout to India". That were my thoughs.