Note: This is long, if you don't want to read it, I'd recommend you hit the back button now to refrain from making posts about the conspicuous length of the thread.
Secondly, As a disclaimer, please note that everything I am going to say and, for that matter, everything on this thread is my personal opinion and experience, But that does NOT mean that you have to agree with me. I will also preface this by stating that I am no stranger to the discussion of what makes an RPG exclusively multiplayer or single player as I've been playing role-playing games (both single and multiplayer) for nearly two decades now. So, I have experience with both sides of this argument. I have also taken the time to read many other opinions on the web and forums, with many of whom who have personally have given me their common agreement on many of the points I've made with them. So without further adieu, let me begin.
As I'm sure you all know, there has always seemed to have been quite a crowd for a Bethesda game to contain some form of multiplayer or co-op mode for eons now. Looking back on the Oblivion and Skyrim Co-Op mods, the popularity of some of these cooperative modifications certainly has brought quite a lot demand for some sort of implementation of multiplayer added into the games. Personally, I myself have always favored the possibility of a cooperative fallout experience, and have looked to older games like Halo & Borderlands as prime examples of games that have pulled it off without breaking the good experience. Now, before anyone makes any interrogatives, let me be concise about what exactly it is that I'm referring to. In Halo, (like in Fallout 3) you were that lone-wolf persona who worked typically by himself to achieve his goals. However, if you wanted, you could always have one of your mates hop in and play as a non-cannon character with you. This had no impact on the story whatsoever. Now some of you may say that with a game like fallout that contains a VATS and dialogue system, pulling something like co-op would be impossible or would require a complete rework of the game's integrity (like quests, vats, story, etc) but with other games out there that can sure enhance an experience with the inclusion of co-op, let me tell you that it is very possible to do all of this without breaking that 'lone-wondery' feel to the game.
For Borderlands, the game can be played alone, but can also support four players playing co-operatively online or over LAN. (To address the compromising of questing) the game follows the progress of the host player, rewarding the other active players for completion of quests for their characters. If the other players are doing the same quests in their campaign, the completed quests remain the same in their campaign as well as the host's. When more players are present, the game alters the statistics of the generated enemies, balancing the game due to the larger number of players.
With the new fully voiced dialogue quest system we have, I feel that this could flow in nicely if the other players could hear what was going on. Furthermore, with the new base & town building we've seen, what wouldn't make the experience even better than some fellow friends to help you build and defend your settlement? Now, onto the other problem with vats. For VATS, I look towards Red Dead Redemption as my solution to this problem. In Red Dead Redemption a similar 'dead eye' system exists where the player can slow down time to select certain parts of a body (like in fallout) and when ready, confirm their actions and fire short bursts at the unlucky soul. To keep this effect in multiplayer without breaking anything, dead eye still remained with the exception of the removal of slowing down time. Rather, you could still mark body parts on targets, but time would just flow normally; it worked out very nicely.
If you're the kind of person who doesn't care for Co-Op and prefers that lone-wolf feel, then be my guest. I can the many reasons why many of you would feel that Fallout should remain a single player game. On the other hand, I also feel that a cooperative option to accommodate both parties would also attract more people to the game. Such an option would allow both, single player and co-operative guys, to play their games without the fear of their type of gamestyle being imposed upon. Let's be real here, there really aren't too many Co-Op RPGs out there in the genre, and I really find that unfortunate since I would have loved share my experiences in games like Might & Magic or in The Elder Scrolls with my buds of mine. Rather, what exists is a plethora of MMOs that if I want to game together, I have to play on a massive server and pay a subscription fee for full access of the game to enjoy it what it has to completely offer.
All-in-All, I really feel the company should take one final look at the possibility of adding a co-op system to this game. It would really be a great experience to quest with your friend or defend a settlement that both you and your buddy of yours set up. Furthermore, it would be a nice addition to the lax selection of Co-Op RPGs we have out there at the moment as a gaming community. Nevertheless, I'd like to hear what you have to say and look forward to hearing from you all soon.