Madness Video Game?

Warning crazy idea here.
          So I have a science fiction story called Madness (working title (probably won't change until like publication)). In Madness there is mention of the Death Runner structure. It's not super important to the story, just enough to outline some of the interactions between the Devil and the former Black Knight. But I can see it being deeper than that.

          I'd like to develop a game that walks someone through the Death Runner experience. With complete player customization. From body to clothes to weapons. Complete freedom. Well, they'd have to choose their body type first and then it is locked in place. Other things would be more or less permanent like real like, such as hair, tattoos, or scars. But I would work hard to get a balanced weapon system going so that knives could be as viable as guns but you could have strange weapons too. And you gain proficiency (better stats) for the weapons that you use more.
          It would be somewhat Grand Theft Auto like in the sense that you'd be offered missions to get cash, but the battle system would be a little different. You wouldn't have access to your weapons in normal walk around mode except in certain circumstances or missions. But you can challenge other Death Runners to battle. A typical battle is set up with a bet and weapon selection. You are either immediately ready or have some time to get to the battle field. During battle, there is a locked area around the battle field but it would be a pretty big area. Start out on either end and then work to the middle. You can get your opponent to surrender or go for the kill. There would be rewards for either and it would affect your rank.
          Ranks would be determined by battle wins/losses and surrenders/kills. Rank affects what missions you get. You can challenge without regard to rank but some Death Runners won't fight you, like if you are way above them or too below them. Others will take you on no matter what so even as a newbie you can take on an experienced. Your Watcher will probably tell you that it's stupid and not to. Well if you chose a good Watcher.
          A Watcher is like your manager. You get one at the beginning of the game based on series of questions the player will answer. You can hire or find other Watchers later in the game to give you a choice of whether or not to change who watches over you, gets you information for missions, who guides you in battle, who records your battles, who offers guidance. Again, I want a lot of variety here.
          You'd have other characters that you could bring into your 'team' as you get to higher levels like a weapons manager or a hacker or a physical trainer or a doctor or a public relations expert. With any team member you set up expectation and give them tasks. Mostly they'll be on a payroll so you don't get them until you are high enough rank to do payout missions. Sometimes you'd find characters that overlap occupations like you could have a Watcher who is a weapons manager or a doctor who helps with the training.
          Training would help temporarily boost stats. But unlike proficiency, these stats wouldn't lock into place. If you don't use your fast muscles, they aren't as fast. So you have to set up a training regimen that builds up the stats for your character that you want. Over time, if you work on a certain stat long enough, the base value will increase. Like if you always hit the weights then yes, your strength will be higher than someone who always hits the treadmill for stamina or agility courses for speed. Having a personal trainer will help boost stats and reduce the time necessary to get those stats.
          So the mechanics and set up of the city/world would be heavily based in Madness but what about plot? Would there be a series of missions that lead to something? A series of events triggered by being in the right place at the wrong (right) time? An end goal of getting out of Death Running alive? How important would plot be? Would the focus be on the story, on surviving, or being the very best? I don't know.
All I know is that there would be a huge amount of variety and sandboxing between what the player can do, who they can interact with, how they get to the top. I mean, I want the most open, realistic world possible. It would be massive. And I also want it to be based on the player's skill and management.
          Sigh. This would be awesome.