Sven above makes great points. Also some kerbs are not designed to be driven in wrong way. A sawtooth kerb like I\I\I\I\I\I\I\ is going to be pretty violent in wrong direction. And that could create some surprising and difficult physics issues to solve. Just tire blowouts could increase massively if the sim looks at the 3d shape of the kerbs when driving over them. That in turn could create public talk about the sim having weird issues where actually the issue is somewhat realistic. Apart from fixing those serrated kerbs I don't see how to avoid them becoming an issue if the game has the capability to look at the kerb shape and have it cause tire issues.
You also need ai lines for the reversed tracks, you can not just invert the existing ai lines. Start lights are also pointing in wrong direction and start grid needs to be made new. Or maybe flipping them around. Flipping the timing gates is probably a piece of cake and could be done inside the code without even needing separate layouts. Some areas of the track would also need adjustments to track cut limits.
All that being said I'd really like to see reverse layouts of existing tracks. For online racing it would easily add new configs at very little effort. The safety aspects don't matter in sims and crash barriers being dangerous don't matter in sims at all. I know live for speed has reverse tracks but it is also important to remember that those tracks are designed to be driven in both directions. Very few real life tracks are. Personally I'd love to see reverse tracks but there are some difficult problems to solve.