Back in the day, Battletech was running with a storyline where there was great technology, but years of warfare lead to factories and research centres being bombed, new developments arising, and the cycle continuing again. Warhammer 40k has a similar premise in it's background.
All the weapons used at the time of play are shadows of awesome technologies, either cut down to make them more efficient and easier to repair on the battlefield, or simply degraded because no-one remembered how to create the awesomeness anymore. It's a common idea in post apocalyptic games and fiction (in Rifts, no one human can build a suit of armour that matches the glory of the Glitter Boy), it also appears across the sword and sorcery genre (where great weapons of the Atlanteansor other lost empires are powerful relics in a darkened age).
I'm thinking about the same thing for the game tentatively entitled The Carcosa Golem Shuffle.
When the war began, psychic technologies and mystically enchanted construction drones were adapted to battle. Such tools were awesome for their original tasks, but no so much for fighting...thus they were modified, sometimes successfully, sometimes not. Over time, the original designs were lost, the workshops building the early models were destroyed in cataclysmic magical firefights (on some occasions as targets, and on other occasions as accidental collateral damage). A decade into the fighting, so much magical energy was sapped from the environment tht the great portals to the mythic homelands ceased to function. The mortal fighters we left cobbling together the bits on the streets, making ad hoc war golems from the normally incompatible parts from various empires. Generic jury rigged parts had the advantage that they could be attached to most other technologies, but the disadvantage tht they were no longer "pure" and lacked some of the refinements and subtle edges provided by original manufactured parts.
On rare occasions, a mastercrafter might have gained access to an original part, and might have managed to reverse engineer the enchantments...this finding a way to add them into one of their generic components. But more often than not, when this occurred there was an unexpected glitch in the end product.
As the last fanatics fight over the ruins of the city, the enchantments binding the golems become unstable. Every time a local power node is liberated from one band of warriors by another, sparks of power trigger the psychic neural matrixes empowering the golems with artificial intelligence. This may awaken free thinking golems (such as the player characters), or may reset originally programming, unleashing golems unthinkingly loyal to their original faction looking to enact the final mission they were assigned when they previously lost power.
This basically sets up the notion that the characters are all cobbled together golems. The game begins when a power node is reset, and they are awakened with consciousness. They may awaken to find a group has claimed their power node, but more likely both sides have wiped each other out in a deadly conflict of attrition. The battle would have drained the node, and only hours/days later would it have rebuilt enough charge to trigger the golems in it's vicinity. The characters would be surrounded by spare parts, with which they could construct the best possible versions of themselves. But there are probably better parts out there, in the ruins of the city, possibly guarded by similarly awakened golems, or by some of the last remaining mortals defending their strongholds and rebuilt workshops.
The Golems gain energy from the power nodes, but the mortals were draining the power nodes at a far greater rate for their battle. Now that the mortals are all but wiped out, the nodes are gradually rebuilding their charges. Things may still be conflicted now, but they are relatively peaceful compared to the new onslaught that will rain down apon the city when the ancient portals to the mortal homelands reactivate. Before that happens, the characters will need to choose a side with whom they can make a stand, or gain enough upgrades and power to make a stand of their own and declare the city a territory of their own.
This feels like it's heading somewhere fun, I'm not sure if I'm retreading ground that others have already explored. I hope there's enough of an interesting spin on it to give it a fresh outlook.