All of this can be done in theory but you would 1.) Be the first to do so and 2.) You'd look at years of hard and possibly frustrating work.
Not only will you need scripting but you will probably also learn basic modeling and animating which are tough skills to master.
Take my advice: Get started with a simpler game idea to check if its even your cup of tea. If you happen to be displeased with GG, try the other engines as well. Its best to get into a big project like this with some experience under your belt.
Its like driving, you don't just get into a car and cruise through rush hour traffic, you learn the traffic rules first etc.
Quote: " if the drug dealer wants to sell stolen items to the pawn shop. He gets money added to his wallet. If the cops catch him, he will get money deducted for fines,etc."
This is a good example. Here you will need a dynamic script that takes all these variables into account. If you want the characters to interact with the player in any meaningful way you will have to animate them which is an entire job in itself. You'd need to learn quite a lot of external software such as 3Ds max or similar too.
-Wolf