I already started my campaign a while ago, using Cyberpunk 2020 with considerable modifications to match Mistborn as a setting.
My premise was that Ruin managed to escape his prison and swap places with Preservation, turning the helpful mists into clouds of choking miasma that grow worse over time. The Lord Ruler, recognizing the threat, was forced to release some of the technology he'd been suppressing, leaping the technology level of the world up several notches all at once. Needing manpower and fast, both skaa and nobles were trained in engineering in labor camps and set to work building massive zeppelins whose weight and size defied all logic as the floated up into the sky.
Most of the Central Dominance escaped death before the miasma became lethal, the noble houses each in charge of their own airborne colony. The nobles, armies and inquisitors were equipped with gunpowder weaponry to defend themselves in the skies, ranging from muskets to Gatling guns and other Civil War era artillery, and higher grade technology was set aside for the Steel Inquisition's personal use. But the sudden introduction of trained engineers among the populace paved the way for innovation and advancement, and as the Lord Ruler is now trapped his tower in Luthadel - built to tower above the miasma but located behind the curtains and geysers of miasma escaping from the ashmounts - the technology is spreading, and making revolution a more intriguing prospect.
The mountains of Terris, which rise above the miasma along with other large hills and mountains, are now the center of commerce and the only major land-bound branch of the Empire. Elsewhere, pirates and other freelancers who managed to build or acquire airships of their own harry supply ships sent between the slow-moving colonies, and in vented underground caverns beneath the miasma the Survivor's army builds its strength in preparation for a time to strike. The Lord Ruler's control of technology and information has been broken, but his power has not.
As for how it's going . . . pretty good, actually. Lurchers are way more useful on airships/planes than Coinshots, surprisingly enough, as Coinshots have so little mobility without ground to anchor themselves on. The technology gaps - Civil War weapons and transport with Medieval weaponry and accommodations being just as common - makes for an interesting patchwork society where changes in location and privilege can make the players feel like they're jumping through time. I'm still deciding whether I want to keep with the hyper-realistic Cyberpunk 2020 houseruled game I'm running, or if I want to convert it to this, but either way it should be a lot of fun as it continues on.