The following thread on the official forum allows us to vote for feature changes in the game. Developers are aware of the thread. Below I've listed my 3 votes and a few others I would choose with more votes. The first post in the thread contains mostly great ideas throughout.
http://forum.projectcarsgame.com/showthread.php?35783-Your-top-3-suggestions-rankings-in-OP
My top 3
1 Weather control - variable duration of slots, real drying, wetting times while fast weather changes, randomizing career weather
2 Replay director - TV like replay with timings, progress bars, slow mo, few camera angles for a track spot (randomized or determined on the fly) (include driver name and telemetry data available when spectating)
3 Allow us to finish qualifying lap when time runs out
Here are some others I like the look of but really there are some great suggestions throughout.
Custom Championship for offline (Select cars, tracks, number of rounds)
Naming, saving, restoring and sharing setup files
Custom livery manager - online/ manage lots of liveries, assign liveries to AI (including console)
Improved replays + markers" to allow jumping to specific points in the replay
In a session, allow host to have 2 races, with the second race having reversed grid