1) How The Fantasy Would Have Happened

In order to resolve this minor plot hole, Steven Moffat brings back John Barrowman, David Tennant, Matt Smith, Billie Piper, Alex Kingston, and that chick who played the french behind-the-scenes-queen. Donna remembers, Rory be badass, and everybody lives (some don't even have to die first).

Then you wake up to the proper fictional reality.

2) How The Spin-off Would Have Happened

River is in 21st Century Cardiff, doing something badass (like leaving dirty notes in time and space for her husband). Something evil attacks, they save the Earth, and River unlocks Jack's Vortex manipulator, though in an untrusting fashion because neither are quite sure who the other is except that cryptic hints and significant looks into the distance can only mean some connection to the Doctor. They find they have amazing on-screen chemistry and proceed to travel through time and space slinging innuendoes and oozing angst and UST.

Then, the Library happens. River tells him not to interfere just before dying. Jack is devastated and slightly betrayed. The audience is devastated and slightly betrayed, because dammit the feels. Jack returns to Cardiff, commits suicide until he feels better, then re-locks his Vortex Manipulator and leaves it with a note at UNIT's secret HQ, swearing off any sort of fancy Vortex nonsense, because it just brings angst and far less sex than it's worth.

Instead, he time travels the old fashioned way. And becomes a giant telepathic head. Eventually.

3) How The Slash-fic Would Have Happened

The Doctor arrives at Torchwood, bloody, broken, possibly sexually assaulted by scientists or prison guards or tentacles. Jack slowly heals him, forcing the Doctor to confront his trauma in a climax that peaks with the Doctor confessing that he can no longer fight his true feelings for Jack (or maybe just the sex pollen), so just fuck me already ooooh yeah. . .

Then they have totally awesome sex, despite the Doctor being a nervous-ass virgin. The story should then come to a satisfying end.

But instead, there's 52k words of m-preg, unnecessary angst and a very disturbing birth scene, before abruptly cutting off during a shopping trip at Toys-R-Us.

The Vortex manipulator escaped to UNIT custody after killing Jack 500 words into the marshmallow angst. At least it won't have to endure any baby barf on top of the spunk stains.

Someone forgets about the giant telepathic head bit.

5) How Karma Would Have Happened

UNIT follows Jack around until he dies. They steal the Vortex manipulator and use a scan of Jack's eye to "sign" a bequeathment contract for him. They also steal his clothes, because fuck Torchwood.

Jack wakes up. He's a little confused, but also naked, so assumes something good must have happened. He shrugs the incident off, grabs his spare manipulator, and bumps uglies with aliens in bars. Tentacles are likely involved.

One of them gives him a V-STI, which slowly turns him into a giant telepathic head.

6) How It Probably Would Have Happened

The TARDIS lands in Cardiff.

"Hey, sexy."

"Yes, yes she is. By the way, give your Vortex Manipulator to UNIT."

"Why?"

"Timey Wimey."

"Well . . . okay. Love the bowtie by the way. I remember this one time. . ."

The TARDIS leaves.

The giant telepathic head is very sad.

7) How The Short Version Happened

It was really John Hart's. Jack would never.

8) How Having No Wrists Would Cause It To Happen

Jack became a giant telepathic head. Giant telepathic heads have no wrists to attach a Vortex Manipulator to, so, knowing the entire story behind the return of Gallifrey (you know things after a few million years), buys a Tesalecta and programs it to hang around UNIT in 2013, being dashing and heroic until something kills "Jack," allowing for a conveniently timed bequeathment.

Jack then donates the Tesalecta to a non-profit branch of the 51st Century Justice Department.

You know things after a few million years.