WP8 apps can resume from the start screen or app list now... only catch is that the app has to be updated for this to work. It's an easy upgrade, but still - would be nice if this were also a feature in 7.8.
Fast app resumeWindows Phone 8 introduces the ability for apps to request that user actions that would typically relaunch the app, such as tapping the app?s Start Tile, instead resume the suspended instance of the suspended app instance, if one exists. This feature is called Fast Resume.