A lot of current threads on the board are coming together. Here's my 2 bob. Action Force were unique and can never be replaced, but - just maybe - added to.
Perhaps that's why AF were so perfectly conceived - imaginatively based on a small core of successful Cold War CRW and other conventional forces (GSG, SAS Oman-Embassy-Falklands, Falklands infantry) confronting a rabid enemy who distilled the precepts of Cold War revolutionary war from many different areas into an abstract ideology to which a full spectrum response was required from AF!! The Baron was a marketing genius?.
Out of the seemingly experimental mini-Action Man first AF range some genius realised they could create a whole toy range that a series of good guys could be grounded in recent events schoolkids (particularly in Britain) were familiar with and thus seemed realistic (Oman etc. Falklands, - even one of the adverts has a tracking shot which looks like a long battalion stick snaking out as they march up Mount Kent or any South Atlantic hillock, an image familiar to many of us in that era) with some imaginative add ons (Q (presumably for fighting Mr Matey at bathtime) & Space for some soon to-be-confirmed enemy opponent whilst facing an enemy who obviously looked evil, twisted and oh so diabolical from their obscure satorial tastes, colour scheme, preferrence for the cyrillic alphabet [and thus, being Soviet-influenced, obviously very, very bad indeed] and groovy eccentric hardware which, it must be said, did include quite a bit of weaponry so presumably packed a punch. And Palitoy could re-use some moulds at the same time. Wizard.
And that was just before the next issue with the fantastical Roboskull, Escape Armour, Hyena, Kraken and beloved Skeletron which really beefed up the ranks and confirmed the Shads as a bunch of determined crazy terrorists bent on world domination. You could imagine the Baron - part Baader-Meinhofesque doctrinaire 70s terrorist/mad scientist/unstoppable epic Bond villain (hence the creation of AF) - finalising his latest Kraken cloning plan alongside his latest plan to take over obscure islands in the Pacific whilst ordering a new batch of skeletron limbs from his preferred supplier and firing his Uzi at some minion or AF intruder at the same time. Any scenario was viable. Besides, in the real world stuff was still kicking off, Europe was still cut in half, Middle East was at war, terrorists were active all over Western Europe. Megalomaniacs were still out there! Ultimately, "the Enemy" had just enough referents to make them believable whilst being completely unique.
Ok, so with the new range for AF there was at last something for Space Force to do, Q as well (assuming Krakens had some transport and Skeletrons could swim...). The toys made for Space and Q in the next issue were pretty neat and the range seemed to be building up momentum... but the rest is history.
As mentioned at the beginning, Z & SAS were grounded in a reality of images and stories that made them believable and made kids identify with them. Plus with their size it was more like organising model soldier full-on war on the order of British Airborne Division vs. SS Divisions in full scale Market Garden mode than dressing Action Man up for another tete-a-tete with Cindy or whatever was meant to be done with them but without the hassle of getting the Humbrol out and painting the model figures for 10 weeks before getting ready to kick off the festivities with full satisfaction ...
Z just got better with the APC, a great derirative of Soviet/WarPac kit. Kick ass hardware that fitted with everything else when you sat wondering why the Lord allowed the Attack Cannon to be invented (apart from indirect observed fire). And you could always go to Argos to fantasise about buying the Z Force Base but never really quite afford it.
As was mentioned, the attention to detail on the range on items such as the wheels are really made to make them special (also good on all surfaces (perfect for the home)) you really have the impression someone took care to devise all the add-ons, stickers etc.
Although SAS were great, I didn't really see how Blades and Wolverine fitted in to the original range but they still worked somehow. Stakeout & co. seemed more suited to hard graft on the Jebel Akhdar or sitting in an OP or wherever, the last ditch run up a mountainside with jimpy on back against the fiendish Shad infantry.
Along with BAF there was an epic narrative to create an explore with all the different personalities, capabilities and hardware so when we got home for tea after school the battle was ready to go. BAF seamlessly integrated the AF universe into the hard-nosed do or die epic narratives of Commando, Battle, Tiger and Eagle comics where the enemy was always ruthless and the often doomed protagonists had to knuckle down and get on with it. Back in those days fiddling with an Airfix kit was enough to precipitate grandparents and their old muckers into reminiscences about putting jerry to the knife in some night contact at Tobruk, various Nips during Chindit ops, or SS arbeiters during Market Garden alongside local doughty resistance, so the stories didn't seem that far from reality. The holidays had an obvious simplicity too - work the paper round to buy AF or just play with them. The diabolical Baron and Black Major could manufacture any intrigue for our intrepid heroes to tackle. The mythic quality is what made them unforgettable.
You can see this when the series "ended" and the Cobra & AF muppeteers came along. How many times did they resurrect the original crew in the pages of BAF? Attack on London, Revenge of the Red Shads, and that story with Firefly vs. SAS in the mountains (at least). The original band appealed to an epic narrative in a way the soulless Duke et al didn't.
But that was the best thing about Action Force - perhaps the point was clearest with the seemingly redundant Q and Space Forces - it was absolutely perfect for our imaginations to run riot when school ended.
Yet this grounding in reality also seemed to stick. Events like the secret war in Bosnia, Freetown ops in 2000 (mamba men anyone?), East Timor infil and the early days of the Afghan intervention were straight out of some AF scenario dreamt up in the winters of 83 and 84. Psychologists probably have a phrase for the concept condition, rendering of reality in pre-adulthood, nostalgic reflection back on it when reality mirrors pre-adulthood imagination of reality. Hmm, an AF imaginative parallax.
And their enduring appeal is testimony to their AFs eternal appeal for the imaginative (and great build quality!). I kept mine as a teenager because I realised kids would still love this stuff in years to come. And on this very site we see members dragging the kit out of the attic and letting their children enjoy playing with it 20 years on. AF forever ma-aaa-an...
Here endeth the lesson....
Yours slotting the Red Shads,
PS. The AT-AT was really invented by

Paint it red and you'll see what I mean.

"Eagle, I am your father!"

"Noooohhhh....."

"And I am your brother!"

"And I either got malletted in a European central front double envelopment in depth desant exercise or got crocked in Afghanistan even if I look like it was at Goose Green"

"Muppet that thou art..."
On that note anyone who ever took their AF and parachuted them into a Star Wars scenario with their greatest toyshop rivals the fantastical superhero status of AF was always confirmed. Boba Fett vs. Quickfire? Eagle vs. Greebo? No contest. SAS win EVERY time.
PPS One day we could write a blow-by-blow account of AF aesthetics. Imaginative, Philosophical, (A)historical and Literary if anyone so inquired.