To say that the SimCity launch has not gone smoothly would be an understatement. Two chief complaints have been the lack of an offline mode amid server issues, and the generally small city sizes. One intrepid modder has killed both of those pesky birds with one stone, and argues that it shows EA could easily pull it off too.
A YouTube video posted to Reddit (via Eurogamer) shows the game running in debug mode. He notes that not all of the debug tools are enabled in the consumer version, but it did let him edit the highways outside of the city boundaries. He claims this means editing outside of the boundaries is potentially viable. On top of that, he disabled the disconnect timer, saying "the simulation can carry on with no connection indefinitely." This removes the ability to save/sync or use region-related features.
The official SimCity Twitter recently posted conflicting messages about the possibility of an offline mode. The company has assured users that the launch issues are nearly over, and EA has promised a free game to affected users.