I think - feature-wise - F1 2020 stands out. Its jam packed full of content and has a very fun driving model both with wheel and controller. I love the fact it has historical championships, own team championships, single grand prix, loads of practice and qualifying options, time trial mode with ghosts, rivals and leaderboards. This combined with project cars would be great.
An unusual feature I would like to see (although may not work in reality) is some kind of pit stop mini game where you have to kind of do the pit stop things in real time. These would be influenced by the staff you hire and tech you invested in etc.
The main draw for project cars 2 for me was perfecting laps with different car/track combos and working up the leaderboards. After having a second child I had to sacrifice my triple screen/vr rig so now I exclusively play project cars 3 and F1 2020 with a controller which means my driving game priorities have changed somewhat!
Controller handling, race/time trial customization and car collecting/customizing are my new wishlist items (hence my current love of PC3). If PC2 had PC3 controller handling and car collecting it would be my perfect game. If a developer could essentially make a fully featured Project Cars game that had the feature set of F1-2020 and a truly great "Sim/Arcade" choice where both handling options were perfect I'd be a very happy driver.