I have a few ideas for the mod, and if u like some of it, its will be good to see in the mod.

[1.] Working windscreen wiper when u press a button on the panel

[2.] The lifetime of the engine of the car would decrease after a continuous usage, there would be more together with this the engine would be the consumption of fuel and environment filth one at the same time.

[3.] Cars have a dirty level - u need to clean it with soap and water.

[4.] World actually reacts on vehicles - mobs get scared and try to get out of the way of vehicles.

[5.] Some visible and functional things like in Crayfish vehicle mod.

((Examples)):
Petrol pistol which can be unhooked.
Car's key visible in the car interior and the key needed to start the car.

[6.] You mentioned that accomplishing the break of the cars would be very heavy earlier. It how feasible, if the car would shatter so only like in Crayfish vehicle mod's car damage system?

Anyway, with a joy supplies it, the mod develops from day to day. Keep up the good work and another many successes!

[1.] Working windscreen wiper when u press a button on the panel
Already a thing, but pack creators have to actually make wipers. None of them do, so that's why you don't see this.

[2.] The lifetime of the engine of the car would decrease after a continuous usage, there would be more together with this the engine would be the consumption of fuel and environment filth one at the same time.
Again, this is already a thing. If you don't use creative engines you'll see this.

[3.] Cars have a dirty level - u need to clean it with soap and water.
Has been considered, but pack authors don't want to make a second texture. If you can convince them, then it's possible.

[4.] World actually reacts on vehicles - mobs get scared and try to get out of the way of vehicles.
Not going to happen. That requires changing mob AI, which isn't possible with how Vanilla MC is coded.

[5.] Some visible and functional things like in Crayfish vehicle mod.
Not interested in such visible things. For one, most people don't even understand the keys I do have, nor care to use them. They just want to jump into the vehicle and call it good. For another, the fuel pumps are pack-based, so I can't go and have a fuel nozzle for all of them as they all have different nozzles and hoses. In general, what Crayfish does doesn't work for IV, as Crayfish doesn't have multiple people making multiple vehicles. It's only him, and so he gets to make the models compliant with his features.