This thread is relevant to my interests. There is a strong likelihood that the restoration of Shurima will be the next major Factions storyline. (Factions is a community game mode where stories based around the Institute of War develop in response to actual outcomes of faction vs. faction matches.) The following is written from a Factions perspective, but that's pretty close to just "League with a League in it".
Basically: if Azir makes his play to restore Shurima to full statehood, the League will be instrumental in his efforts. If he just walked out and revealed the power to restore Shurima, Noxus would be there in two seconds flat to beat him up for his lunch money ("nice artifacts! we'll take those"), assuming that Demacia didn't get there first to lock down all this heretical magic and set up a puppet regime. Recognition as a League member-state would give Shurima a chance to maintain its sovereignty. He would need to seek out allies in the League to support the fledgling state, and would have to recruit Summoners and Champions to represent Shurima in the battles on the Fields of Justice (and possibly off the Fields) that would surely ensue.
From an out-of-universe perspective, I think the League really adds a lot to this story. Without the League, either Azir gets his new "empire" conquered right off the bat, or else the authors handwave a sudden surge of power that takes Shurima from "random wasteland" to a massive empire capable of fighting off Demacia and Noxus. To me, that feels like a cop-out. With the League, it becomes a political story that brings in many different Valoranian nations as Azir seeks allies in his fight to keep Shurima free. There's some real excitement there: Will he succeed? Will he fail? And if Shurima does emerge as a sovereign state, what will it look like? What tradeoffs will Azir have to make in that battle? Which Valoranian states will become allies of the new Shurima, and which will become enemies? I just find that much, much more interesting than "and then Azir does some magic and Shurima is back just like it used to be."
Anyway, I added some background below. Very draft-ish.
For a long time now, Shurima has been Council territory. Nobody was that interested in it. Other than the Floating Pyramids, there wasn't much to Shurima but a bunch of poor nomads and a lot of sand. Several Shuriman Champions are in the League, but Shurima is nowhere close to being a member-state.
24 CLE: The Hextech Revolution
The first major upset occurred in 24 CLE, prior to Azir's return, when the discovery of Void-tainted "dark sand" in Shurima catalyzed the so-called Hextech Revolution. The dark sand ("pyrikhos" in Shuriman) was created when the Void's energy mixed with the lingering enchantments of the ruined Shuriman civilization to create a versatile and abundant hextech energy source. Whereas before hextech devices had been hand-crafted with rare, specialized components, this dark sand seemed capable of powering virtually any hextech design, allowing for true mass production. The Shuriman dispute culminated in the Battle of Shurima, when Demacia launched an illegal attack on Zaun's pyrikhos mines. It was discovered that the mines had been built on top of a ruined temple built by a cult of Xerath, and the dimension-warping magic restored hundreds of these cultists to life.
Zaun emerged from the Shuriman dispute with ownership of much of Shurima's territory. It continued to mine the pyrikhos, but an alliance with Xerath has begun to expose Zaunite mages to the deeper mysteries of Shuriman magic, long thought lost.
24 CLE: Azir enters the League of Legends
Azir entered the League of Legends in the wake of this catastrophe. Although he makes no secret of his intention to become emperor of a new Shurima, he is by and large not taken very seriously. Shurima is still mostly owned by Zaunite megacorporations, and they do not seem interested in talking with some crazy bird-man who wanders the desert claiming to be Emperor. He starts talking to Summoners and other Champions, recruiting those he deems worthy to his cause.
25 CLE: The return of Shurima
If we do a Shuriman storyline, it will probably open with Azir using a spell to lift the Shuriman ruins up out of the sand. Suddenly, everyone realizes that he's not just some delusional bird-man lost in the past, but indeed someone with real power. Immediately, he would have to find a way to fend off Demacia and Noxus, who are now very interested in what's going on there. The League might grant provisional member-state status to Shurima while the matter is investigated and adjudicated; very possibly, League emissaries would be stopping Noxian legions and Demacian knights in their tracks just outside the borders with their "hear ye and be warned" proclamations.
At that point, the clock is ticking. Azir will have to choose his allies carefully. Under pressure from Demacia and Noxus, it's quite likely that the League would not be able to maintain an absolute truce for long; fighting might well break out here and there. While Azir is battling for Shurima's sovereignty, others will very likely be trying to use the League's dispute process to carve Shurima up into protectorates. There are endless possibilities as to where the story might go from there.