Spirit of the Century is a popular setting for FATE. You can check out the popularity of the FATE 3.0 Kickstarter
over here.
Yes, Unisystem could be implemented via the Authoring Kit. Technically, every game system we already support, including horribly complex ones like Pathfinder & Shadowrun, can be implemented via the Authoring Kit. The Kit provides the same framework and tools we use in-house.
