Posted on several other sites, to ask for crits and suggestions. Working on concept art. Will start making the models, textures, and animations. Still no idea what engine to choose. Read *featurelist* below.

Call of the Elders
Singleplayer/Co-Op modification/game, First-Person perspective.
Design Document

Basic premise:
The game/mod is played preferably in co-op. The theme is survival horror, deviating from the genres usual dark levels filled with zombies, and instead focusing on THE survival horror.
CoF is about being frightened, and trying to survive impossible odds, without firing too much at zombies.
This game/mod will borrow a lot from the works of Howard Lovecraft, since it is the feeling of impending doom, destruction and despair that is the core of all of his most famous works.

Players can start playing a campaign together, exploring large, very surreal environments in search of forbidden knowledge, and ultimately a way to escape unspeakable evils that guard it.
The setting is modern day, since not a lot of reserach is required for that, and the mod team will be deviating from the works of Lovecraft enough to stay clear of copyright issues.
There will be guns, tools, and magical items, the use of which should be discovered by the players during gameplay.
More emphasis on solving puzzles, reading ancient texts, and surviving cultists, magic and monsters, than slaying hordes of zombies.

Episodic content is the key to releasing this game/mod. Levels come in sets of 3 or more, linked together in a campaign.
Each such campaign will last more than 2-3 hours of gameplay, and will eventually lead to a semi-cliffhanger ending,
which will compell the players to wait for the release of the following campaign, or even join the dev team to help out with the production.

Level design is what should be emphasized the most.
Concepts of fantastic surreal landscapes, inspired by Lovecrafts books, where even the art would make you want to look deeper in the environment,
explore caves, read ancient tomes, battle enemies too strange to describe. There should be more to this than just bland caves, boring cities, and uninspired cultist hangouts.

You will still be fighting off monsters. That would be done with anything you can lay your hands on.
There will be plenty of fun and awesome weapons, but also a few very clumsy objects that were not intended to be used to cause harm.
This will give the player a choice to either fight with whatever he has, or run from the things chasing him.
Running, will also be an option, as long as you can lock the doors behind you and escape.
Certain enemies will be programmed to be immortal, or too strong for a small band of adventurers to slay, and therefore must be avoided somehow.
This will be a big focal point of the puzzles that the players will be solving: getting from point A to point B, without being eaten by some horrible entity that sits inbetween the said locations.

To list other possible features, i will mention an RPG-like system, where the players will acquire skills, items, and abilities,
depending on what they did during the previous levels of the campaign.
For instance, reading a certain book will make a player go seemingly insane,
and not use any weapons/items/magic, but see magically-concealed enemies, secret passages, and descipher ancient texts.
This ability will stay with the player throughout the campaign, and will affect the playing style of him and the rest of the party.

About "getting stuck with a puzzle" now. Any of you played any Metal Gear games? Notice that when you get stuck and don't know what to do, you can call your superiors on the "codec" and they give you helpful tips. What about a similar system, but minus the codec and the superiors? Picture the situation:
Players enter a room, where they find several switches and several doors. The switches have several weird symbols written on them. So have the doors. The players dont get what to do, so each of them presses the "say idea" button, which is conveniently mapped to the Q key on the keyboard. This will make the players' characters say out loud what they think should be done. For instance, an Archeologist character might refer to the strange scroll with similar lettering the party found earlier, and suggest that the player holding it would try desciphering the symbols on the walls, using the scroll with the code on. Such codes could be randomized every time the game restarts, and with render-to-texture technology, the symbols on the switches and similar contraptions can also be altered. No direct solutions to the problem are given, but mere hints to what the players should try. Different characters with different acquired skills should say different things in situations as this. I will need many voice actors.

Now about "disconnecting player". If a player does disconnect without wanting to, all his things are dropped to the ground, and can be shared amongst the party of adventurers. His "magic skills" are left visualised as objects, such as crystal orbs, or floating lights. All these can be picked up and used by other players, so they can progress through the level even suffering the loss of an important character with vital skills to the current quest.

Players suffer different "death" depending on type of damage they were dealt. Players killed by monsters in combat, may be revived later by either a medic, or by a magic ritual. Players slain by wicked magics return to the party as semi-visible ghosts, with several new abilities and drawbacks: seeing invisible monsters, being able to posess friendly characters for benefits, casting special spells, etc.

Can Doom3/Q4 do this?
Few monsters, Co-Op with 3-5 players? Fairly large indoor/cave/underground/dungeon enviros?