Yeah, I've spent many hours playing different mods and never noticed the scale difference until I started comparing models in the editor a few days ago. It doesn't really bother me personally, but I want to hear other opinions on the subject as changing the size of the model messes up the lights setup.
I've also decided to simply replace the LA mod model files with my own instead of trying to figure how to properly set up a car. I still hope to figure it out along the way but right now I felt like I lost a lot of time for very little to show for. Renaming my files like the ones in the mod and moving around the child objects a bit in the editor and I had a fully working patrol car in under 15 minutes. Definitely the way to go for the time being. I'll replace all the other Crown Vics in the LA mod then I'll start modeling a new car,
I hope it will be alright if I release a car pack that overwrites some of the LA mod files but it will still require having the base mod installed in the first place.
Here is how the new CVPI looks like. I've decided to go with ~110% of the scale that's in the LA mod. (the lights are not place correctly as my car is slightly bigger than the original one)