The Endeavour mod menu has some clothing options. I used it to get the Cop Outfit, working in Online and SP. IDK how the trainer actually works though. I have minimal coding experience. So we know its possible. Its might be as simple as changing "Cop_Outfit.mdl" to "whateever.mdl" in the trainers source code. Now its just getting the source code or even a partial source code, and finding out what the outfits model name is.