How would Sion's lore work now? (Stupid theory)
There's plenty of different heroes whose lores need to be changed after a different heroes VGU, but Sion in particular seems like a bit of a mess.
So far, we know that he was the original Hand of Noxus, who killed Jarvan I when Jarvan laid Siege to Noxus (Demacia Rework makes them more isolationist? Did they really lay siege to Noxus?), that he too, died in that battle, and was brought back by the Black Rose (Darkwill was an ally? Manipulation?).
Then, Swain seems to have found records of him in "Old Noxus", brought him back with Jarvan's blood (first gathered for a publicity stunt for a league that no longer exists?), and revived him as a blunt instrument....despite having Darius's loyalty...almost as if he knew Darius wouldn't approve of the latest set of heads to remove?
Except now, with Swain opposed to the Black Rose, it doesn't work anymore. not in the old way.
Well, there is probably a way to make it work.
Like Rome, it is possible that Noxus was not always so seemingly impenetrable. A commander who cared sufficiently little for their troops, like Hannibal, could suicide march them through terrain others would see as impassible, or in some other way, gain the upper hand, including a power that was militarily weaker than Noxus itself (as Noxus doesn't seem to have a major military rival as of right now).
Noxus, with most of it's armies on the field, with only hot-headed, glory-seeking nobles to lead and fight, is on the back foot. Boram Darkwill having died fighting the invader (Still Demacia? Ionia? Barbarians from the Frelijord? Demons possibly? Darkin?), and the young Keiran is not up to the task of saving Noxus.
And then Sion appears.
In this incarnation, Sion was not originally the Hand of Noxus (else he too would have been sent on campaign), but a common peasant soldier of great strength, charisma, and tactical acumen. He'd singlehandedly stalemate the efforts of whoever was invading Noxus's heartland. In light of this, Keiran would grant him the title of Hand of Noxus.
In time, the invader finally starts laying siege to Noxus, and faced with starvation and an overwhelming force, Sion led his men in one desperate charge, and claimed his foes life. This much plays out much the same as in Canon. > While others counseled me to bar the gates and force our foes to fight for every inch of Noxian soil, this man demanded we march out and face them. He would not cower behind the city walls while Noxus' enemies still drew breath. With our warriors at his back, het strode as a giant through the Demacian rabble with one clear purpose: to cut their army's head from its body.
>Jarvan's royal guardsmen believed they could halt his charge. They were wrong. He cut them down, one by one, until only he and the king remained. Battered and fatigued, any lesser man would have given up the attack, but he was a true son of Noxus. He battled Jarvan beyond the point of breaking and was finally bested... but not beaten. With his dying breath, he locked his fingers around the king's throat and broke the will of a nation.
Sion dies, Noxus is saved, and Keiran, insecure and with nobles plotting for his death, deals with the Black Rose to revive Sion.
The rest goes more or less as it does in the current canon, with Sion becoming a mindless beast. Keiran has him hidden in the Statue, Noxus is under the Black rose's thrall.
Until Darius and Swain start kicking out all the corruption and making Noxus GREAT AGAIN. But this time, it's not Swain that roses Sion.
It's the black rose itself. Needing some way to hold onto power, and lacking the strength to face Swain or Darius openly, they release Sion and manipulate him.
What happens next? Who knows. This isn't even canon to begin with.