Is it possible to make users own gun models, ammunition and vehicle for UEFN in Q4?

I am currently researching UEFN, and I noticed that Epic Games will support for making the creater own item in Q4.
However, the definition of the Item is unclear, does it include a Car model or just a gun shape?

So, I would like to know more if there is a way to change car models to own skeletal mesh or replace mesh in the future.

Thanks