You know what FM5 really needs? Double Decker racing like what was shown on Top Gear. You take two vehicles, stack one on top of the other and get two drivers. One to control the steering and one to control the gas/brake. It would be a fun little game that I think would be awesome to have with the Top Gear mix that is included with the Forza series.
You know what? We have a thread for posts like these: Forza Motorsport 5 Game Features Wish List