So uh I made a template to make an addon mod, only for vehicles at the moment. I also include detailed explanation of any files and specific section needed to be edited to make an addon vehicles work. but the problem is, I'm not sure if I had covered all resources that the game used (for example, type of tuning parts and so on) due to a lot of files need to be checked and less time to work on it. now if you know much about this, let's collaborate or something?
and sorry I can't attach the template files for now, in case there are some people use it for their own advantages. but I'm sure I'll share it even beta version of it later.