^Indeed, good luck
But, since the topic has already been necro'd, I think it might merit some discussion. Off the top of my head some mechanical and design challenges I can see:
-3D and all the fun that comes with it
-3D code. I personally haven't looked into the d3d_ functions too much, but they seem to have their own set of peculiarities(As far as the way they interact with each other, having to set Gamemaker up to work with them first, all the different transformations, etc.) If you're already a pro using the 3D capabilities of Gamemaker I presume this isn't as much of a challenge, but I'd wager a lot of people here stick to 2D.
-3D modeling. Much like above this is more of a specialty kind of thing, but it is something to account for.
-You'd almost have to create your own sound engine to take care of keeping track of wildlife and other players, as well as to create a more immersive feel so you would probably want to have the game keep track of whether the player is in an encounter or not and modulate the music/background noise accordingly.
-Hunger, a simple variable in each player that goes down over time and can be replenished by eating food, right? Oh wait, where do you find food again? Let's say hunting and/or gathering fruit from plants. Now you have to code in systems for those, including basic animal AI and possibly food growing back over time.
-Combat, a mainstay for Hunger Games and video games in general really.
-Some form of stealth system, possibly just involving noise reduction but could quickly become more complex than that.
-I would assume you'd want some basic inventory for weapons and healing items.
-A big point of The Hunger Games is that not only are you in a free-for-all but the environment itself is extremely hostile. So you'd want dynamic events occurring throughout gameplay such as the environment shifting around or a pack of genetically modified animals or extremely poisonous plants your character can eat by mistake(not really dynamic, but part of the hostile environment thing).
-I like the idea of controlling the arena through the gamesmaster perspective. That could be fun, but once again introduces it's own issues of balancing with the rest of the gameplay and making it engaging enough that players want to play it(or just make it optional)
-Managing scope and feature creep would be a challenge with this. In this post alone I've thought of several "Ooh, wouldn't it be cool if..." ideas and discarded them before this post lost practicality.
This didn't even go into multiplayer and what challenges that brings to the table, and if you're doing singleplayer and multiplayer the difficulty goes exponentially up. I'm honestly not a big Hunger Games fan(I've read the books, but my memory of them is somewhat hazy) However, I think that a well done video game could be a good play, so I'd like to see if anyone else has opinions on this/cool gameplay ideas. I personally have no plan to pursue it as a project, honestly it's quite beyond me at the moment but it's always good to test the design muscles