I'm at the opposite end of this.
I want Horizon to be it's own game, to have it's own identity to be honest. Apart from the cars, i'd like everything else to be different, unique.
The one big problem I had with Horizon, is that it felt too familiar. I want PG to differentiate themselves from Turn 10 even though it's part of Dan's vision for the franchise. PG have enough talent and experience to hold their own imo..
Anyway, I want to see more sanctioned race types and shows to happen at the actual Hub. Drag racing events, drift events, show'n'shine..etc. Kind of like what Black Box did with NFS Pro Street.
I also want to see a deeper customization and upgrades feature. Car culture is really varied and ideas are really wild. There are some crazy and imaginative modifications, (body/paint/performance) done with cars these days.
It'll be interesting to see where the next location will be. All I know is, it better not be Colorado..