Techinically i'm not sure about whether it's legal or not. I've been thinking about it for a bit of time now. It's illegal to own the game. It's illegal for other people to own the game but I mean is it illegal to uploads mods to an illegal game?

Chances are, yes. I mean if you had marijuana in your house it's illegal to own or to sell/give out. So could you modify the bong and sell it online legally?