Maybe you can set the default in there but that wasn’t what I was talking about.
Lets say a vehicle has 5 bumpers and it spawns with its stock bumper. To change to a different bumper, which is specific for that vehicle, you need to use a GTA5 native function.
Peds work in the exact same way with their different components.
If the model you are talking about has these extra addons you just need to change it via the correct native. Instead of creating your own system I’d recommend you just use a server side trainer that supports custom models.