Excited for this one! Hoping for more tire and wheel customization, like painting letters on tires any color you want, on any tire compound, and on each individual tire. Maybe even a simple livery editor on tires. Would also be cool to put different wheels on each corner of the car, and be able to paint each wheel individually. Something I've always wanted to be able to do. I haven't played much Horizon in a while, so maybe there is a more finite customization on the wheels and tires now, but just something I'd like to see. It has gradually gotten better and better as time has gone on, so maybe it's finally time.
Something else I'd love to see is a customizable instant replay editor. The replays in the Horizon games (and Forza in general) have never been that great. I think in Horizon they are usually chase cams that just follow the car around and rotate around the car. No interesting viewpoints and panning angles. Again, I haven't played in a while, so maybe they have made the replays more interesting since I've last played.
But anyway, I'd love a mode where you can go about placing cameras in different locations during the span of the replay session and setting up the view points that you want, like camera height, camera angle, make it fixed or pan with the car, etc... Maybe different exposure or color mixes too. Would just make it more interesting. Could make for some cool movie-style chases and drift sessions. You could be your own film director. That would just be fun. If anyone remembers playing Driv3r back in the day, it had a custom replay editor. I loved making movies with that mode. I made some epic police chase movies!