Turbo: I’m thinking the first thing we need is to handle why some technologies are working and some aren’t. So, how are certain technologies being suppressed? The whole thing could be a simulation, where physics would be easy to rewrite (haha, after getting control of whatever’s damping the technology, our heroes “wake up” from a simulated shared dream and have to deal with reality!) or nanotechnology that absolutely suffuses the environment and breaks anything that looks like technology, provided it doesn’t have the correct passcodes. Gotta make sure those ancient LARPers weren’t cheating.
Dan: Reality suppression and nanotech’s been done. What if we go the MMORPG rout and have cheaters get punished by game avatars? A huge robot angel descends from the sky (or claws its way out of the ground and runs at you, or builds itself out of machinery or animal and plantlife in your area) and smacks you when you use proscribed technology. Or just have orbital lasers blast anything producing electromagnetism or moving more than 100mph (although that’s been done too: Daybreak Zero and Souls in the Great Machine).
Making the technology interdiction mechanical will set limits on it, which the characters can get around in interesting, plot-making ways.
Turbo: No matter how the control system defines “high tech” there’s going to be ways around it. Maybe you can make a mechanical computer, but not transistors (http://en.wikipedia.org/wiki/Mechanical_computer). You can make a pulse jet (http://en.wikipedia.org/wiki/Pulse_jet ) that runs on booze (I think ethanol would work, not super sure though) but since nice bearings aren’t allowed a regular jet engine is out of the picture. That sort of thing.
If the Parliamentarians are curious and clever enough, they might be able to counter the ancient supertechnologies and magic of the Imperial House. They’d still be horribly outmatched, but they could have some tricks up their sleeve!
Dan: Shielded electronics? Steam-punk technology driven by atomic piles? A human force of secret police who follow the angels’ orders to seek out and destroy technology based on their own best judgment? A sort of armed Luddite Inquisition? Is that what the Krypteria is??
Michael: How to give things a mythical spin? Use Clarke’s third law. The AI’s have gone rampant (http://en.wikipedia.org/wiki/Rampancy#Rampancy) so a few thousand years later people say the spirits of the land are in rebellion. Certain nanotech works if you know how to hack the system. Sorcery! Certain programmes are going in self-perpetuating loops. Cursed magic swords! There’s a lot of potential McGuffins in that last one.
Things get interesting once you throw away super-tech hand-waving. Then the limits placed on technology are works of Man, not God, and might be circumvented. Also it drives home the thematic point that the difference between magic and technology isn’t the level of advancement (despite what Clark might have said) it’s the understanding of the user. It’s a magic sword in the hands of a church-ordained paladin, but a semi-sentient nanotechnological tool in the (hopefully gloved) hands of an engineer. And I say the engineer’s way of understanding is better.