Dont be fooled by hyped features.
If it where to be a "readymade" gamelogic, it would be pretty much just usefull for
this certain gameplay.
Modding an existing game is totally different to making one.
In a mod, you have an already running game, and just change the content it runs.
But the gamelogic takes professional teams years to make. The content on the other hand
can be relatively easy changed as the tools and contentparts are already made and tested.

Creating games from scratch is hard work, and requires more experience than just
skills in Modding content. And noone will seriously make you a GTA type game
for free.