nice to see someone has similar idea to my old one
In my vision of such feature:
1. Player has to buy a TOOL.
Why not download for free? Inmature content. When buying, most people would be willing to make something worthy.
2. You have 4 categories:
In each categorie, there are up to 4 slots for customs
3. Player has to sign up a contract with some ifruit internet agency, then is able to sell his/her products.
the price is X , authors gets 5-10%.
Why like that- becouse ingame inflation is something that we just should roll with it, and stop complaining (its not my game).