I wouldn’t have written Shadowlands at all.
But…if we have to.
First, I would change the nature of the Maw entirely. Instead of a realm of coordinated Mawsworn, the Maw is a realm of chaos. Zovaal was the Arbiter once not because of his fair judgment but because of his insatiable need for knowledge which he absorbed from each soul that passed by his judgment. Alas, insatiable means insatiable, and in a bid to learn more he stepped beyond his station, beyond the realm of death. He made to join the Shadowlands with reality, to absorb the knowledge of all realms and timelines, and become unto a true god.
He was stopped by the other Sepulcrists. His power was taken and used to create the Maw in the first place, binding him to it utterly. Unable to escape, unable to see beyond its limits, unable to learn as he had before. He ‘rules’ the Maw in name only. In truth it’s a realm of anarchy with the worst souls that ever existed constantly fighting amongst themselves, being born and reborn over and over again. You might see one or two carve a small niche of power, a citadel here, an outpost there, but such positions are fleeting and could be here one day and gone the next.
Zovaal however, doesn’t care about any of that. He dwells solely in Torghast and only dreams of finding a way to wrench his essence from the Maw’s chains and return to his rightful place. Torghast is Zovaal’s tower and sanctuary, but also his laboratory, the creatures contained within the results of his experiments and the chaotic magic that flows through the realm.
Instead of a big bad, Zovaal is a bit-player, one unassociated with Sylvanas whatsoever. He’s a threat, however, because more souls are going into the Maw and if he draws power from them, the Sepulcrists fear that Zovaal could free himself, and in so doing pose a threat to the weakened Shadowlands.
Killing Zovaal destroys the Maw. It’s still there for gameplay purposes but in lore we purge it. What happens to all the souls that we didn’t rescue before doing so? It remains unclear. Ooh, mystery! Maybe they got obliterated, maybe they got re-judged by the Arbiter, maybe they flew away to the far edges of the Shadowlands. Maybe some or all of the above.
The deactivation of the Arbiter wasn’t due to Argus’ soul or a plan eons in the making, it was Denathrius, who - ever the ambitious one - had finally tired of sharing leadership of the Shadowlands with his ‘siblings’. Without the order of the Arbiter, the souls are drawn to the chaos of the Maw. Denathrius created the drought specifically so that he could make use of his stockpile of anima to overpower them and crown himself absolute ruler. He remains the prime villain of 9.0, as the most proximal threat.
The Forsworn aren’t influenced by the Mawsworn, they’re a natural result of the Kyrians.
The Maldraxxian infighting isn’t due to any untoward influence, it’s a natural result of the culture they’ve built up over the years. The Primus isn’t captured, he’s in hiding, observing, watching to see how Maldraxxus changes like a sociopathic child tugging at the wings of a fly.
Sylvanas remains a villain, and most of our exposure in the zones is us following her trail as she undermines the order of the Shadowlands. Bastion is the first zone we do still, and we meet Sylvanas (or see a vision of her) in which she explicitly states her problems: The Shadowlands is corrupt, its beuracracy evil, and she’s going to tear it all down. At times it seems like she is deliberately leading the player character (wrecking ball that they are) towards specific aspects of the Shadowlands so that they can see it’s broken.
She did still kidnap the faction leaders, in order to draw the player character in and make sure they followed. You are, after all, her trump card. Even if she’s unsuccessful, you’ll finish the job for her.
This comes to a head in 9.1 where we face her down, and kill her for her crimes past and present. She dies smiling, not smug, but satisfied, because 9.2 is fixing the Shadowlands. We dismantle the Covenants, either by force or by the leaders accepting the folly of their plans. No longer would souls be judged, instead they will drift in the aetherial sea vast realms going where their heart draws them, and then we seal it, for good, forever.
The knock on effect is that once a soul passes through the Veil, to enter the Shadowlands proper, they are gone for good. Resurrections? Better be quick or no dice. Sapient undead? Basically impossible to create new ones unless it’s immediate. Calling up spirits? Not likely bucko.
The Forsaken are now an explicitly endangered species and can’t replenish their numbers. No new Death Knights either. This realm is the only one we have. The realm of death is sealed.
…in lore, at least. Obviously they’re not gonna lock it off for gameplay purposes.