Let me paint for you, just for a moment, a nightmarish scenario to compare with the hellish visions seen in HR Giger’s Necronom IV, the Swiss surrealist painter’s inspiration for his later work on the hideous xenomorphs in 1979’s Alien.

Imagine for a moment that George Lucas, not long after Disney hired JJ Abrams to direct the first new Star Wars movie in more than a decade – perhaps even after the release of that first teaser trailer for The Force Awakens, which sent everyone into apoplexies of expectation – found something in the small print that allowed him to change his mind about handing over the long-running space saga to a bunch of newbies.

Phones suddenly buzz in Tinseltown, frowns are seen erupting on the foreheads of Mouse House lawyers, and within days the creator of Luke Skywalker and Darth Vader announces that the whole darn $4.05bn sale of Lucasfilm to Disney is off. Instead, Star Wars fans can look forward to a Lucas-scripted spin-off about Jar Jar Binks’ ongoing political battle with the Trade Federation.

Fortunately for Star Wars fans, gorgeous George remains locked out of the Jedi braintrust. But a similar dynamic of huge anticipation followed by crushing disappointment has been playing out for real among Alien acolytes over the past year or so. Ridley Scott’s middling Prometheus may not have been the Phantom Menace of Alien prequels, but compared with Neill Blomkamp’s uber fan-friendly pitch for a belated sequel to 1986’s Aliens starring Sigourney Weaver and Michael “I wanna introduce you to a very personal friend of mine” Biehn, it might as well have been.

Blomkamp’s Alien concept was very nearly the Deadpool of sci-fi movies, resurrected by 20th Century Fox from Hollywood development hell after the film-maker began posting concept art for an “abandoned film” featuring Weaver as Ripley, Biehn as Corporal Dwayne Hicks, and an all-new take on Giger’s famous xenomorphs on Instagram. The internet went into predictable meltdown and the District 9 director dramatically announced in February last year that the studio had given him permission to move ahead.

Then Scott, like some terrifying party-pooping alien critter bursting out of fun’s chest cavity, stepped in to make it clear that his own Alien movie, a sequel to Prometheus now titled Alien: Covenant, must take priority. So instead of a Weaver-led movie from one of Hollywood’s most promising young science fiction film-makers aimed at restoring the saga to its pre-Alien 3 glory, we face the prospect of another portentous pseudo-origin story about mankind’s connections to the xenomorphs and their utterly tedious extra-terrestrial “Engineer” creators. Or if things go really badly, another three movies on said subject matter.

“Ridley asked Neill not to make our Alien ’til after Prometheus 2,” confirms Weaver in new comments published by Indiewire. “He wanted his movie to shoot and be released first. But [our Alien film is] an amazing script, and Neill and I are really excited about doing it ... It’s just going to take a little bit longer to get out to you, but it’ll be worth the wait.”

So why is Blomkamp’s movie a more attractive prospect than Scott’s, especially when the veteran British film-maker kicked off the entire slasher-in-space subgenre with 1979’s searingly superb Alien? The answer lies in Weaver’s return and the pitching of the new movie at the point just before the long-running sci-fi saga began to haemorrhage all credibility.

In the real world, David Fincher’s Alien 3 – by no means a terrible film, yet hardly one which makes any real argument for its own existence – debuted in 1992, followed by the ersatz afterthought of Jean-Pierre Jeunet’s Alien Resurrection (complete with clone Ripley and her half-xenomorph “child”) in 1997. Let’s not even mention the two execrable Alien vs Predator spin-offs.

But in Blomkamp’s wonderful new fantasy timeline, these movies never happened. With the slate miraculously wiped clean (no one knows quite how, and the film-maker himself partially backtracked on his own promise at one point), Ripley and Hicks can set off for new adventures after destroying the xenomorph-infested planetoid at the end of James Cameron’s Aliens (it was, after all, the only way to be sure). There might even have been space to bring back poor little Newt, the tough little orphan girl who many fans never forgave Fincher for killing off at the start of Alien 3.

In the grand pantheon of great Ripley moments, almost all emanate from the first two Alien films. The warrant officer’s beautifully bleak sign-off after destroying the final xenomorph in Alien; her sweary mecha-suited battle with the giant queen in Aliens. These are performances unparalled across three famous genres: action, horror and science fiction.

Meanwhile, Alien Covenant will offer us a film set on a mysterious planet (possibly the Engineer’s home world), where Michael Fassbender’s David the android has been kicking his heels for 10 years waiting for a new human crew, led by Katherine Waterston, to turn up. There will be xenomorphs this time, but you get the impression Scott only agreed to include the monstrous beasties as a result of the popularity surrounding Blomkamp’s concept. As recently as 2014, he was still indicating that Giger’s creations were gone forever.

Star Wars began to get back on track when it brought back centrepiece figures from the hugely popular original trilogy to inject The Force Awakens with some much-needed authenticity. Now it’s time for Alien to follow suit.

If the saga has any hope of getting back to its own 70s and 80s high point, it surely needs to bring the original all-action Hollywood scream queen along for the ride. Then fire up the afterburners and nuke the rotting corpse of Alien: Covenant from space.