I find FPS combat to be lacking in this game, so I'm going to experiment and create a module specifically for making FO3 more like a FPS (only in terms of ranged combat, I don't have any desire to get rid of any of its RPG elements). Anyways any pointers would be appreciated, I'll put some of my questions and a point list of what I want to do.

Q: How do I tweak the game's AI? I have the motivation to study the language used and Bethesda's scripts.

Q: I do my modelling with 3DS Max 2011. I'm guessing the chance is next to nothing that the appropriate plug-ins/exporters/importers exist for this, so what programs should I use in conjunction with it (for exporting the models to and animating with).

Aims

-More ammo
-Segmented health bar with regenerating chunks (similar to the health systems used in Halo 1 and the Riddike games).
-More enemies, less health, less accuracy, less experience for killing them.
-More/better movement animations (fast run, roll, run jump, fall/jump landings, etc).
-Enemies make more extensive use of cover.
-Disabled VATS
-Better AI


Thanks for reading

Engine can't handle all of that.

To give you a more precise response.

1 - The only tweaking you can do to AI is what packages they use, and their combat style. As to how they execute said packages, that is entirely hardcoded and unchangable.

- You can easily add lots of ammo to all the leveled lists within the game that spawn items in containers, and on people.
- You could not do a segmented health bar. You could make it recharge, and possibly replace the HUD texture for it, but it would funtion the same way technically.
- Alot of this is also hardcoded. You would have to manually add more enemies to the game, you could reduce health (but it would be slow and painstaking), you could reduce each weapons accuracy manually. Experience is hardcoded so this could not be done.
- The actual slots these animations take place is hardcoded, so you could at best replace the current ones, but not add new ones. (Like running jump, or fast run, roll, etc)
- This has to do with the combat style, which you could tweak to get this effect.
- I'm not sure this can be done. I have tried, but its a hardcoded function of the game.
- Again, beyond Combat style, this cannot be done as its all hardcoded.

I hope this answeres some of your questions. You could do a little bit of what your doing, but as a whole idea, its simply beyond the game engine.

to me it really sounds like you might want to get another game

Sprint Mod for FO3 introduced a "fast run" mechanic - holster your weapon and sprint in short bursts - uses AP.
XP can be adjusted also by changing the level-up requirements. If you can't change how much XP a kill gives you, change how much XP it takes to level up.
Acrobatics - rolling, etc. - don't know that this is possible - same with lean-in lean-out cover. Some of that would be hardcoded. Some of it would require creating new animations, which everyone says is a gigantic pain - even people who pull off complicated mods say that.

For examples of what can and has been done, check out FWE for FO3 (Sprint Mod, Grenade Hotkey, some HUD changes, Bullet Time and more all integrated), Arwen's Tweaks mods for FO3 (contains a lot of AI changes) and FNV, MMM for FO3 (adds enemies),