From a future Cybertron, a small band of Predacon criminals (led by a wannabe crime boss calling himself "Megatron") have escaped the planet aboard a stolen ship. Out in space, the recently-appointed sergeant Optimus Primal of Maximal law enforcement is on a nearby moon or planetoid training a few cadets new to the force. Their training exercises are interrupted when a call from Maximal Command orders their vessel, the Axalon, to pursue the escaped Predacon convicts, as Primal's ship is the closest vessel to intercept the Preds.
Sergeant Primal and his cadets take off in pursuit and manage to catch up to the Predacon ship. But a brief skirmish in space creates a transwarp accident that sends the two ships back in time to crash-land on an organic planet that would later on be revealed to be Earth, and where they all scan beast modes based on the planet's various animals, insects, and dinosaur remains. No stasis pods in this version, though. They are all on their own.
And this time, while they initially find no humans in the area, as they begin to explore more and more of the surrounding forest that has become the main setting for the battles between these Maximals and Predacons, they gradually begin to discover traces of a remote civilization. Dirt roads cut through the forest, stone bridges and wooden bridges built across rivers and lakes, a village of shops, houses, and other buildings made of wood and stone, and even a great castle with a drawbridge and moat overlooking the village, making this a small kingdom. It is not prehistoric Earth, but medieval Earth, in the age of knights and kingdoms across Europe.
But one question still remains: If this small human kingdom exists, what happened to the humans who built it and lived there? That would remain a mystery, which probably wouldn't be solved until the end of the first season. Were the humans to return by the second season, that would allow us to see how the Maximals and Predacons would interact with humans, since unlike Autobots and Decepticons they are not giant robots, and humans of the Middle Ages would react much differently from modern-day humans to the existence of extraterrestrials who could change into Earth animals/insects/dinosaurs/etc. (especially to those with dinosaur beast modes).
Also, the Autobot/Decepticon legacy has no significant role in this story, so no appearances of Starscream's ghost, the Ark and its stasis-locked occupants, the Nemesis, etc. Just the Maximals and Predacons and whatever else they come across in this medieval time period. Though, being a BW-original concept, a new version of the Vok (or the Skriix, or even a different alien race altogether) could still play a role, possibly being the answer to the humans' mysterious absence in the first season.
While Primal and Megatron would still be the leaders, the remaining casts of Maximals and Predacons would be a bit different. For instance, since I don't think any new take on Dinobot could ever live up to the original, I'd leave him out of this entirely and instead do something new by having Wolfang be the Predacon-turned-Maximal of this story, since his mold ended up having both Maximal and Predacon releases. The Maximals would start off with Optimus, Airazor, and Cheetor from the show, and two more who would be new characters, one male and one female, to make five at the start. The Predacons would have Megatron, Tarantulas, and Waspinator from the show, plus Wolfang (before he switches sides) and two more to make seven (Wolfang's defection would then make an even six on both sides).
The Transmetals would be a very different concept still inspired by the original but done in a new way. By the time of the humans' return to the story and the Maximals finding allies in them (which would actually take a while due to deceptions and machinations caused by Megatron that would prevent any immediate human/Maximal alliances), the two species would work together to build new suits of armor for the Maximals to wear in their beast modes, to essentially make them like knights. Said armor would be specifically designed to resemble the look of the Transmetals of the original series. Though, since this armor would only resemble the Transmetals in beast mode, their armored-up robot modes would look radically different from how the Transmetal robot modes looked.
In a further Transmetal homage, Megatron would have a different design in this series that would be like a cross between his pre-Transmetal and Transmetal designs. Picture his Transmetal robot mode, but in the color scheme of his pre-Transmetal form. His fake T-Rex head torso is also replaced by his pre-transmetal torso. Though, he does not have his VTOL fans since his beast mode is just his normal pre-Transmetal purple T-Rex form, meaning all of his beast mode parts in robot mode (like his lower legs and his shoulder panels) would be scaly purple instead of metallic bronze. And while he would have two normal arms and hands in this design, the T-Rex head of his beast mode would be able to be pulled out from where it is stored on his back and held in his right hand as a laser gun that wraps around his wrist to hide his hand inside it, along with his tail still being held in his left hand as a shield/lance/whatever-kind-of-weapon.
But while I'd be getting rid of Transmetals as total body upgrades, I would still keep Megatron's dragon form upgrade, but only as an end-of-series final form upgrade that would be the main instrument of his endgame, instead of how the original series had him get that form and then decide to use something completely unrelated to it (the Nemesis) as his final trump card. In this version, the dragon form itself would be that trump card, in his bid to become the most powerful Predacon in existence, in an unholy grand ascension.
The Fuzors would also be a bit different in concept. In this version, only the Predacons would become Fuzors because they would be the result of Tarantulas conducting genetic experimentation on his fellow Predacons to upgrade them into new composite beast mode forms. One such Fuzor could be a majestic-looking griffin Fuzor, while another could be something more hideous and gruesome like a bat/scorpion Fuzor, something that the medieval humans would definitely mistake for a demon.
In a loose homage to both the Dinobot clones and the episode "Dark Designs" from the original show, at some later point in the story, Wolfang would be captured by the Preds and forcibly experimented on in a cruel attempt to turn him back to their side, turned into a horrific cyborg that would also pay homage to the Max-B toy, now repurposed as this mutilated cybernetic form of Wolfang. He'd eventually break free of his reprogramming and rejoin the Maximals, but would have to go living with his disfigured new form and the mental scars it would leave him with.
All of this would make a distinction between the Maximals upgrading themselves by forging both armor and alliances with the humans while the Predacons would upgrade themselves through ghoulish experimentation, creating a sort of "Transmetals vs. Fuzors" kind of theme in later parts of the story, with Wolfang's Cyborg Beast form being the closest we'd get to a Transmetal 2 before Megatron would get his dragon form.