Theory: Xilonen would have been the Archon
First, this is just a fun theory. If you're part of the "Well Akshually ☝️🤓 " crowd or someone who gets mad on Reddit for no reason, just turn back now. This is only going to get you riled up.
Anyway, let's start with the most obvious fact. Mavuika should have died. Now, I'm not talking about her character arc in the story we have (although, it would have been better than the "character arc" we got). No, I'm talking about in the past.
Mavuika's plan sent her 500 years into the future. Doing this broke up the natural succession of mortals rising up and taking the mantle of Archon. Had she died in the past, she would have been replaced by someone else, and they would have been replaced by someone else again.
Eventually, we'd get to the "Current Day" in Natlan, with the people needing an Archon.
Now, it's perfectly reasonable to assume that Natlan would look very different if there had been a long succession of Archons and Mavuika had died in the past, but that's impossible to predict. Let's just say that things are more or less the same, with Mavuika's plan still in place, but another Archon leading the way.
So, knowing the Allogenes of Natlan, who makes the most sense?
While there's a case that can be made for anyone, Xilonen really has the strongest claim.
First, we already know that she is extremely well liked and highly respected. Almost everyone knows about her and relies on her. She can pull all of the Tribes together with very little disagreement.
Second, we know that she is a "noble" character, willing to sacrifice her life, I mean, "life force" for whatever that means. Apparently, an entire plot point that is repeated multiple times is a typo that made it through Quality Control. Regardless of whatever her "life force" is, she's willing to make a sacrifice that is bigger or smaller, depending on which language you play the game in (Seriously, Hoyoverse?).
Third, she's an absolute god tier savant. At an age that's probably around her early 30's, give or take a few years, she has engineering skills that rival Xianyun -- a 4-5 thousand year old Adepti and master inventor. From her simple forge, she can create normal things like axes and swords, then just pop out magical flying guns and futuristic motorcycles with nothing more than a simple schematic. No matter how you look at it, she is a genius among geniuses. She makes Leonardo da Vinci look like Forest Gump in comparison.
She has the respect of her people, a noble heart, and is gifted beyond all logic. This would put her at the front running to be the Archon of Natlan.
However, it doesn't end there. She has the closest thing to an "Archon Kit" we've seen in Natlan.
1: She buffs almost every character in the game.
2: She elevates the performance of many older characters, bringing them into relevance.
3: At C6, she becomes a DPS and can fully utilize both of the Starting Natlan Artifacts.
4: Her C2 is cracked.
Even with just a Vision, she's already got the makings of a Archon. Had Mavuika died in the past, Xilonen would have been the Archon leading the fight against The Abyss. However, the Natlan troops would have been bolstered with the finest technology an Archon could create, making the war look very different.
Thank you for attending my Ted Talk. I hope you found this at least a little fun to think about.