So the Idea is to add Chess and board games in general, I for one would be playing it the majority of the time, I personally love chess and are we not all kings and queens my good people? 

Has my idea already been suggested in some form or another before? No it has not I've searched the forum using keywords and nothing of the sort popped up.

What does my idea entail? I'm thinking it'll take a little intrical coding to make a pop up chess screen and leaderboards/rankings. 

How can my idea be successfully implemented into the game as it stands? Perhaps someone has a chess app and would be willing to donate it towards the game and work from there? Otherwise code up a pixelated version of it nothing fancy, 2d will work best as its easier to code up exspecially if bringing in new content if ever needed.
 

What major changes would be needed to make your idea work? Under "Comm" add a new section called "Board Games" The reason under comm is because board games or chess in general is a social sorta activity that people dont often put money on which is why its undewr "Comm" instead of "profit" but that can be left for the players to decide. Also having a section dedicated to  "board Games" leaves room to add checkers, battleships, and connect4 etc.
 

What is the positive impact of my idea? Some of the Greatest Minds in the world strategize over chess, human tactical war history was basically built through chess just diff names throughout the ages. This a world built on war so I believe this may just excel in making the game all the moe intresting as time goes by.

What is the negative impact of my idea? Making more work for the administrative part of the game

How may might my idea affect the rest of the userbase? Will make intellegent people who take the time to study the art.

As a chess lover, I really don't like this idea. Mafia Returns is, in itself, a game. It isn't a platform for games or a social networking site (though some consider it so). The only exception to that is casino games, but those have an RP relevance to the Mafia (though I do have a gripe with credit-based gambling). I don't like features that try to tell the players "we know the grind isn't fun at all, so here's a game to play while you're training!"

Instead, I'd prefer suggestions that come alongside existing features and can serve to make Mafia-based gameplay more exciting, more convenient, or more realistic. And I don't think chess fits that.

Actually, no we are not all Kings and Queens here. You are in the wrong era completely.