Blahblah666: Im thinking about creating a free-to-play FPS title that I think im gonna call GawD mode. Its a Cross over multiplayer and single player (With bots) Quake-style shooter that has a bunch of 90s icons such as: Duke Nukem, Lo Wang from Shadow Warrior, Caleb from Blood, Gordon freeman from Half-Life,Blake Stone, the Doom guy (Doom-slayer) , And even Turok. I've been thinking about this since I was 15 in high school. Ive Been a fan of those Shooters ever since I could remember and i love them to this day. I like how the Doom Slayer and BJ are in Quake Champions and also there is a Doom mod called Samsara, that DOES do this crossover to a certain degree. and another Doom mod called Quake champions: Doom edition that adds Caleb and a few others to the roster.
But I want more.
Like Quake Champions, each character will have there own special ability, that they can activate after enough kills or a time refresh (Im not sure what to implement yet) and each character will have multiple abilities to choose from. Such as the Doom Slayer could activate Bezerk mode-15 Seconds, Acquire the BFG with only 1 shot, or Transform into a Demon-20 seconds. OR Duke Nukem can activate Steroids( Similar to Doomslayers Bezerk), activate HoloDuke, or get a jet pack with a Devastator.
It will be old school in a fasion where you pick up weapons as you traverse the map like the older games, NO Call of duty and battlefield bullshit where you pick what you want before you go to battle. I know you get better weapons and equipment as you level up in those games but im still not a fan, Sorry not sorry. However, each character will have 2 default weapons they can choose from. Some kind of high rate of fire weapon Machine Gun or handgun probably, or a slow rate of fire but more damage weapon such as a shotgun.
Each character will have their own melee weapon
Each character will have at least one map from their own respective games.

And Finally I actually have two questions, how should I develop this? and would I get booted because of copyright infringement? should I just go ahead and make it into another Doom mod? or make it from scratch. Im more than happy to learn to use another engine I dont care how much time it will take I WANT TO MAKE THIS GAME HAPPEN!!!!

kohlrak: There's been talk about copyright reform in europe, so....

Anyway, if a copyright is registered in the US, it is enforceable in the US. If it is not registered, it's not enforceable. There's actually some really interesting and unethical implications of this, but i'm not going to discuss those.

That said, you really, really need to think about what happened to other fan projects like this. Some survive left alone, some are hijacked and supported (megaman street fighter crossover), and some are taken down. I recommend not doing it.

EDIT: Now, if you really want a cool crossover game, there's alot of potential with EF-12, and you might actually be able to have an angle there, and it might even fall under "fair use," but keep in mind you need to stick to american labor for this.