Story concept
Far future. Like, very far future. While the exact year is not defined, a definition would be useless, because mankind has abandoned Earth completely and settled in distant star systems, and both the reference point used (for us the birth of Jesus) and the comparable unit of measurement of time (for us the 365-day year) have both been changed since then. The game opens with the player character - a systems engineer - and the crew of 4 coming out of stasis in their ship in a strange star system, an accident having blasted them off in a random direction from where they were working. The accident knocked out their comms, engines and auto-repair systems, leaving them pretty much on their own, light years from home. Additionally, the date is a total mystery to them, as they have been in stasis for an unknown amount of time. With the ship hurtling towards the star, drawn in by gravity, your crew is forced to grab any equipment and supplies they can and bail in an escape pod as close to a terrestrial body as they can.
With a stroke of luck, the body they land on is a small, rocky body, oxygenated atmosphere, average temperature 10 degrees celsius, about 3.8m/s^2 acceleration of gravity, but otherwise very dry and barren. Scans pick up only the faintest signs of life, but traces of atmopspheric water and evidence of previous habitation. It’s this dessicated, lifeless world that you’re thrust into without warning or instruction. Your other crew members received various injuries in the landing, and you’re the only able-bodied one left, leaving it up to you to scout the landscape for anything that might help.
Gameplay concept
This is a third-person exploration game. The sole aim of the game is to explore the landscape and see what you can find. You have a base - the landing site of the escape pod - from which you operate out of. (I had an idea for a role-playing element where you return to eat/drink/sleep to keep your character from dying while exploring or else take supplies with you, with a story explanation for the infinite supply of food and water, but it can be ditched if found to be frustrating.) You start out with basic equipment - a small buggy to ride around in, your utility suit, and a basic toolkit with a wrench, a large hammer, a laser cutter and a nail gun.
Each of these can be upgraded later on: when you find scrap, you can return it to other crew members, and they can upgrade your stuff. Usagi upgrades your suit with armour, and enhancements like a jetpack, and also wearable gadgets like night vision and X-ray goggles. Denham upgrades your buggy to be faster, sturdier, and fit it with weapons, boosters and other fun toys. And lastly, Schmidt can upgrade your tools, such as putting servo motors in your hammer to get it to hit harder, making your laser cutter longer or the laser more intense, and making your nail gun nastier (you start off with a little pop-gun, by the end you have a machine gun/shotgun combo).
The world is really where all the fun is to be had in designing this game. It may rely quite heavily on dynamic loading that comes with 2.5, but you have a vast open world to explore. A large part of it is just barren plains, but the fun in exploring comes from finding the small exciting parts - interesting landforms, breathtaking vistas, hidden water tables in underground caves, small outcrops of life (a few herbs, a tree in a sheltered spot, or if you’re lucky a wild animal which could be friendly or hostile), or even some ruins of civilisation, from which you salvage scrap and sometimes working stuff. Just developer-side, the twist that the player has to work out from the sparse evidence supplied is that the world they’ve landed on is Mars, approximately 100,000 years from now (about 90,000 of those were spent hurtling through space in stasis).
While the player could just be left as the only sapient life-form on the planet left to wander indefinitely, upgrades and salvage give the player an extra incentive to find stuff. And depending on the size of the map, it could be a very long time before the player upgrades fully - the player might never find everything to be found. This generates rewards for exploring new places other than “hey, look at that view!”. Of course a lot of work would have to go into making all this, but most of it is script-light modelling, texturing and GLSL, which shouldn’t be too hard for a small group of developers to keep at for a wihle. Different developers could work on different sections, which could then be patched together later on. After release the game could even be patched with additional map segments, with new things to be found in them - although you’d have to find where the map segment attaches to the main map first!
What I’m Looking For
Well, if it’s just modelling then what are you looking for help for you say? Well, the truth is, modelling is all I can do in Blender. I’ll definitely need help setting up the character to move around, respond to controls, script the whole upgrades thing, the AI for the few wild animals you do encounter… if possible, and I hope I’m not asking too much, but it’d be nice if I present the concept art for the characters and get programmed characters back, ready to be dumped into the game world. Something like WASD for movement, 1-2-3-4 to switch between hammer, wrench, laser cutter and nail gun, space for jump, enter for action (talk, pick up, interact, etc.), mouse to move camera, click to use tool/fire nail gun/accelerate in the buggy would be ideal. Then, with the core controls and base area in place, any developers who want to contribute would be free to craft their own districts with stuff in them - valleys, ruined cities, mountains, cavern systems, anything! 
How does that sound?
Included the textures themselves in case you want to mess with them.
I’ll think up some ways to develop the characters further, and I’ll throw up some concept art some time soon (maybe even later today!) and you can get to work on the buggy.
