Combining the cars won't take much time and won't increase loading time or anything.
There is no way you can increase the hard coded limit except you can somehow reverse engineer GTAs code and find the parts and edit them. (not easy, just try it...)

Maybe you could also name RagePluginHook, because there are a good amount of people who use RPH for LSPDFR and other mods. (well mainly LSPDFR)
But RPH does a lot of good things like having an auto-updater and the functionality to automatically make backups of your game and reversing game version with ONE Click. It has a console and a lot of development helping things and it works flawless.
I know most people use SHV, but that's also because they never heard of RPH, let people know there is an alternative to SHV and that you can use both at the same time without any problems (that's what I am doing)

@ikt Oh sorry I didn't put the new ScriptHookDotNET files into my GTA folder, i just downloaded them. Sorry!!!

So after I updated ScriptHook V and GTA V I thoug heverything was going to work. But it didn't most scripts stop working when GTA V loads them.

[ERROR] Caught fatal unhandled exception:
System.TypeInitializationException: Der Typeninitialisierer für "GTA.Native.MemoryAccess" has caused an exception. ---> System.NullReferenceException: the object reference was not set to an object instance.
at GTA.Native.MemoryAccess..cctor()
at GTA.Native.MemoryAccess.GetPedHandles(Vector3 position, Single radius)
at GTA.World.GetNearbyPeds(Ped ped, Single radius)
at Cop_Surrender.Class1.OnTick(Object sender, EventArgs e)
at GTA.Script.raise_Tick(Object value0, EventArgs value1)
at GTA.Script.MainLoop()

~~So the reasons are the GTA.Native.MemoryAccess calls, I hope that helps fixing your mods and updating them to the newest version of ScriptHook and GTA V. ~~
I made a mistake, it works when u actually update the dotNET scriptHook, sorry!