LOL--you guys are funny--All of the above listed items could be consolidated into one name---
1. New features----new features such as ammo making and six and others are just simply that--NEW FEATURES.
That is not an improvement.
It could be viewed as an improvement in some peoples minds, but it boils down to opinion.
There is a difference between, New Features, New Improvements, Factual improvements and Opinion Improvements.
Let me rephrase the question.
What new additions or new features are in Fallout New Vegas that could not be added as DLC to Fallout 3?
Ammo making and six and other features listed could have been added in as DLC to Fallout 3.
Give me 3 things that could not be added as DLC and are REAL game improvements...not new features, something that has changed the gameplay so significantly that makes New Vegas improved over Fallout 3.
Well given your comment here, Obsidian could have been given the time to create a whole new game engine with improved character creation, improved NPC AI, improved graphics and all the rest which could be boiled down to the barest terminology of
New Features. So that said, I'd say your argument is self defeating.
As to additions/new features that could not be added as DLC to Fallout 3.
1) The Factions and Factional Reputation System.
2) Traits
3) The Inability to create J.O.N.T.M.O.A. Golding characters
4) Vats no longer equates to Invincibility mode
5) Damage Threshold
6) Gambling
7) Player Craftable and Usable Poisons
To name a few from the ones Styles and myself have both mentioned in this thread. Ok you could argue that they could be added via DLC but would have required a major reworking of Fallout 3's core mechanics.
Edit: If you missed the original list I came up with, it's on page 2 of this thread.