Ok, i really like this mechanics idea, and am not sure if i posted it before, but here it is anyway. This is a FPS, sci/fi game, you are a warrior of the human race, who fights alongside the Alketh against the terrant. As you progress therough a level, you will be marked up on how you complete the game. Factors such as accuracy, deaths, kills, objectives completed, shots fired, and weapons used during gameplay. After this is all factored in, the game will determine your overall difficulty setting and customize the enemy AI to suite you. If you are really good, the enemy will be more defensive and have better weaponry ewarlier in the game. If you do a poor job, your enemy will moch you, fight out in the open and use lesser weaponry for a longer period of time. Second portion of the mechanics deals with levels and weapon upgrades. Certian weapons have attachments that can be fixed, 1-2 of them (not determined) per gun. Now, say you choose a flash light and grenade launcher attachments, you can switch these out, but only when other attachments are readily available to you. You will also be able to shoose the course of your actions, bringing pros and cons into each situation. Maybe the next city you decide to reclaim is a naval key point, but is vulnerable to land attack because of its lack of obstacles, then you will go into the city, meet minimal artillery, naval, and air resistance, but encounter an extremely large mobile armor unit. If you take the city, you get more support in off shore bombardments and naval situations, but you need to destroy that mobile armor unit to get it. Thanks for reading, constructive criticism wanted.

Sounds good. Like many good ideas its a matter of the implementation.

Customizing the enemy AI in the way that you mention should be promising. Max payne did something similar by adjusting the enemy's skill (i.e. accuracy and reaction time) to try and keep you working hard without discouraging you. I thought the games difficulty was pretty consistant and I remember only a few times where i thought the enemies were unreasonably skilled or stupid. Your idea of changing the actual enemies and weapons as more of a story element should be a good improvement, since it is a realistic and not some superficial mechanic made up just to improve gameplay.

You will have to watch out, though, that you accurately gauge the players ability. He may be an excellent sniper, but unable to fight in close-quarters, which might mean that in one outdoor level he cleans up the enemy efficiently, but in the next indoor location he is devastated by able enemies. Hopefully your game is open-ended enough to allow the player to choose their battle environments.

The second part sounds cool. I personally like customization and the kind of dynamic gameplay you want, though many people hate it. Taking strategic locations at the players choice is something usually seen in a multiplayer FPS or Strategy, but that kind of thing is being synthesized into single-player FPS's these days so you're thinking in the right direction.