Polish Fallout fansite Trzynasty Schron has published a lengthy interview with Obsidian's Chris Avellone and Josh Sawyer about the history of the Fallout franchise, their take on Bethesda's Fallout 3, where development of Fallout: New Vegas stands, and more. An excellent read, as expected:
SPECIAL system has been evolving through years - while the differences between the rules in first two games were minor, every next game game of the franchise changed some things - f.e. to include new playable races or to allow playing in real time mode. Working on Van Buren, You wanted to make some major changes too. Could You remind what were the most important ones and explain the reasons for including them?
Josh Sawyer: There were some relatively low-controversy changes like putting all of the skills on a universal starting scale and general tweaks to the attribute system, but the bigger changes had to do with what skills remained and what ones went away. For example, all "gun" skills (Small Guns, Big Guns, Energy Weapons) were rolled into a single Firearms skill. Doctor and First Aid were combined, etc.
My reasoning for combining skills was to balance usefulness across the board and (in the case of the Firearms skill) to reduce general skill list bloat. In retrospect, I also think that having a single Firearms skill would have alleviated the perceived content imbalance between the different weapon skills. I.e. it would be okay to have relatively few energy weapons and big guns if they all went into the general "firearms" pool with small guns making up the bulk of equipment used. Obviously it gives the Firearms-specializing player a lot of tools to work with, but you still can only use one weapon at a time.
The rest of the changes were less obvious, things like removing armor DR/leaving only DT, adjusting perks and traits, and similar tweaks. I tend to favor "strong/all DT, weak/no DR" damage ablation systems because they a) tend to produce results that "feel good" and b) are open-ended.
By "feel good", I mean that good armor makes low damage, high DPS/DPAP weapons seem worthless (because they are) and it makes high damage, low DPS/DPAP weapons feel awesome. Purely percentile reduction systems don't really do either. For this reason, strong DT systems also tend to promote tactical weapon switching based on enemies' armor (or lack thereof).
DR also essentially backs the armor system into a corner, content-wise. You really only have 100 points to play with unless you start introducing weapons that negate DR. The player/enemies are also typically gaining hit points while increasing the DR of their armor, so the damage that weapons have to do in order to threaten the player is enormous. For an example of this, the end of (especially) Fallout 2 tends to fall apart, balance wise, because a lot of battles are settled by double- or triple-damage armor piercing criticals.
Chris Avellone: There were a number of story-specific game mechanics related to your roving adversaries (the other adventuring party) in the game, but that was mostly scripting reactivity and I don't know if it's necessarily a game mechanic. Initially, aside from the added perks, traits, and the mechanics Josh mentions, the plan was you could play as a supermutant or a ghoul as well (and we had sections of Van Buren devoted to those characters with their own level of reactivity). The additional race choices just seemed like a natural extension of the franchise. There was also some evaluation on the limitations of Doctor and First Aid, for example - Doctor had a balancing effect in Fallout 1 because you were under a strict time limit for the game, and using the Doctor skill was fundamentally different than using First Aid because of the time cost associated with it. In Fallout 2, that balance aspect wasn't corrected (no time limit), so we wanted to address that in Fallout 3 if possible. We also wanted to add crafting for Repair, Demolitions, and Science so you could make items, and furthermore, we wanted to change the three-prong quest solution to also include a fourth option: Science Boy (which really hit home after reading the book Lucifer's Hammer - there were instances in that book where knowing basic chemistry and science allowed you to pull off some stunts that were pretty damn helpful in a post-apocalyptic world).
Chris, are there any chances you will join the team responsible for New Vegas after finishing Your work on Alpha Protocol?
Chris Avellone: I'm all done with Alpha Protocol now, it's in good shape. While I work on almost all the projects at Obsidian in some capacity as a Creative Director, Fallout New Vegas is my current focus now. It's great to be working directly on one of my favorite franchises, and it's great to be working with Josh again - he's got great stuff planned, and I think players are going to have a lot of fun in New Vegas.