This is a "Wild Mass Guess" entry, where we pull out all the sanity stops on theorizing. The regular entry on this topic is elsewhere. Please see this programme note.
What might have happened in the other games had they been made.
The game would have started mere hours after the conclusion of LOOM. Only a handful of Rusty's guild manages to escape the Forge, which is now used as a flying castle and weapons munition plant for Chaos. The few smiths who did escape would act as exposition, explaining to the player what had happened, also giving some other insight such as how Rusty's father didn't make it out but is still alive. Before the dead can attack, the guild members would escape.
While they're in hiding and trying to find what to do to free the Forge, there's a strange opening in the Rift and Rusty hears some music, then sees a swan appear before him. It's Bobbin Threadbare, who now has chosen Rusty and Fleece to succeed him in weaving reality. However, Rusty needs to be able to use something musical so one part of the game might be dedicated to gathering materials to make an instrument out of.
Some time, Rusty meets Fleece and several other new characters from other various Guilds. The Shepherds' lands are one of the few safe haven due to some reason. (Potentially because of the concave of clerics having a good faction that was working separate from Mandible and is now working to help clean up the mess he made,)
Rusty, having been dead once, is made an advisor to La Résistance.
Bobbin appears a few times throughout the game to give advice to Rusty and Fleece, teaching them drafts. He also asks one or both of them to recover a black feather that Chaos is holding, but may or may not explain why. Or if h does, the meaning is lost on Rusty or Fleece.
The main objective would be to help raise an army that can take back the Forge from Chaos and the dead. Goals would be to get other Guilds' supports, as they are too disorganized to make a large battle.
Another objective would be to arm Rusty and forge a weapon that can fight back against Chaos and the Dead.
The Dragoness appears before Rusty and makes a Heel-Face Turn. She provides Rusty with some transportation, and assists in the battle.
At some point before the large battle, Rusty would sneak into the Forge and try to get some of the people still living out of it. We see some interaction between him and his father, who is still alive. However I would assume his father sacrifices himself to save Rusty and some other smiths who didn't make it out when Chaos invaded and took the Forge for herself.
Chaos might try and tempt Rusty, recognizing some of the drafts that he is using somehow - it seems that Bobbin has passed on knowledge of some of his abilities to somebody. (Unbeknownst to her he chose Fleece, too, who has learned some drafts offscreen) Not knowing that Rusty cannot actually use some of the drafts like Bobbin, Chaos tries to tempt Rusty, but it fails. He escapes with members of the Guild.
The game ends in a battle that if anything is a Pyrrhic Victory - they won the Forge back, but the world is nearly destroyed and the Guilds have to retreat to lick their wounds again before striking back at Chaos, who had also suffered great losses.
Hetchel's feather might be recovered, or alternatively, Chaos swaps it out for something that becomes personal to Rusty.
However... they set sights on the last safe haven... The Shepherds... This is when The Fold would take place.
The intro would begin during the events of Forge but would be Another Side, Another Story - the intro would show that not long after Rusty goes to form La Résistance, a ghostly swan appears before Fleece this time. He tries to teach her to weave so she can close the rifts without having to have a Swan nearby - having the idea to disguise a weaving stick as a Shepherd's Crook.
The Guilds had become much more disorganized, as a lack of a clear mind had resulted in the Pyrrhic Victory. The Guilds that participated in the battle point fingers and find it harder to trust each other. The Major Goal of this game would be for Fleece to reunite them to banish Chaos.
At the same time, Chaos is encroaching on on of the last sanctuaries. She is also looking for the swans, who occasionally appear to Fleece and Rusty.
Potentially, another goal could be to find Rusty who had gone missing after Forge. He would be in hiding or have gotten lost in unfamiliar territory... possibly sent through a rift to the Outside, where he later wound up... on Weaver Island.
Fleece can see that Rusty is on Weaver Island through a rift through the Outside, but is afraid to go there. She instead tries to find a different way to Weaver Island and finds the dragoness from the previous game nursing her wounds. She helps Fleece there, but Fleece has to bargain and agree for the shepherds to set aside some sheep to fed her.
Once there, some more information is revealed from the other Weavers on how to banish Chaos once more. Fleece must help with closing the rifts and banishing Chaos, along with Rusty. However, Chaos appears, and to escape, they retreat Outside. (She either kills the dragoness or the dragoness manages to escape.)
After retreating through the tear in the Pattern and visiting the area where the swans were in the first game, they make it back where preparations are being made for the final battle. Unfortunately, things don't go as planned.
When all hope seems lost, the Weavers appear with the rift. The final puzzle would be a Call Back to the first game, where Fleece targets the swans and casts the Transcend draft backwards. The Weavers, now back to their mortal state, work with Fleece, Rusty, and any of the survivors to push Chaos back into the rift they carried from the very first game, banishing her once more, possibly for good. Rusty and Fleece get married, and Bobbin becomes the head of the Weavers Guild. Unfortunately, those who died in the battle of the Forge (whose bodies were incinerated) or in the final battle (due to the closing of reality) cannot be restored.
Other random guesses:
The creature that chased Bobbin in the first game reappears as a Brick Joke.
Mandible's spirit appears at some point trying to atone for what he did, thinking how foolish he was.
A few dead people don't envy the living but are glad to be reunited with their loved ones
Some new characters would include people from other Guilds, new Guilds not seen in the first game. Among these would be an actual wizard and possibly a member of the Clergy who had come to investigate Mandible's odd behaviour, thinking he might have tried to overthrow the church.
Cob's spirit might appear and mention Monkey Island... or at least Guybrush.
At some point, Fleece would say "Help me Bobbin Threadbare... you're my only hope."
If the Forge is destroyed, it blows up like the Death Star.
At some point a volcano erupts.
The Dragoness will eventually get over her fear of fire during Forge or The Fold.