I think LFS would benefit if an Open World map would be released.
This doesn't necessarily have to be an all-new map with custom made features.
You could slightly rework the city course, adding more roads, junctions, unlocking parking places and multi-storeys for players to roam free.
We can get server that house substantial amount of people, recreating at least night-time traffic wouldn't be difficult. Possibly add some more space and a motorway around the city, going to some more rural areas with open-rally cross tracks, even if they were just a mash-up of existing RallyX courses.
It would be nice to see bigger vehicles too such as SUV's, pickup trucks and generic trucks for racing.
Lastly, changeable wheel patterns would be amazing, it would add that little bit extra customisation that the game needs and everyone wants - maybe different sizes of the wheels to go with different shapes.
I didn't want to mention Police cars since that's a given - everyone desperately wants police cars and few mods have been done to give players some part of that experience but it would be great if someone incorporated this deeper into the game - specifically Open World would benefit by having Police, fire and medical vehicles as well as the odd pace car and recovery vehicles - even if there was one of each or if they were simply based on slightly modified existing vehicles.
That's just what i think the game needs. The main idea is the Open World, I'm sure everyone would love to roam freely on a true city course as opposed to just generic track-day free riding.