It might be to late for that, but I feel it still needs some attention. To make this short, because I feel it is a highlight that can't be stressed enough and in my opinion nails perfectly what good role playing, dialog and NPCs should be about.
But why is Paarthurnax in particular so interesting? And why should it be used as some kind of reference by Bethesda for Fallout?
Well, before I start, this might be a bit long and it represents my OPINION. I am not writer. I am not some academic. I just describe how I feel about it. I have no clue what kind of intention the writers had with this quest.
Now, I feel that this is so important because Paarthurnax as character and one small quest in particular are very interesting and offering many layers here, of which some might be more obvious than others.
The Situation in Question is:
Kill paarthurnax or not?
Seems easy enough. But in reality it is actually difficult. Most people probably don't kill him, as they see him as likable character, which is understandable. From his introduction by the greybeards and the first time you talk to him he is represented in a very interesting way. He has personality. Because he has a background that was build up. - Not something that I can say about the many other NPCs. But I digress!
The first thing is, both groups have reasonable arguments. They have realistic motivations. It is possible to understand both groups. The Greybeards protect him for his teachings and his wisdom. The Blades want to punish him for his crimes and because he is a Dragon which have been responsible for a lot of unspeakable atrocities.
So It simply isn't about clearly good vs. evil here.
But there is more to this. For example the effects if you decide to kill him or to spare him. The effects of your decision are very subtle. Now I have no clue if that was the intention or not, but it highlights why subtle effects can be just as effective in story telling like to give the player some epic pad on his shoulder or telling him that he now kicked the puppy - or kitten, to show that he's REALLY evil.
If you spare his life, the blades will refuse to give you their full support. If you kill him, the greybeards will do the same. Though, both factions will continue to work with you, though not FOR you. They respect your title, not your personality. This is in my opinion, very good story telling. I would describe this even as fridge logic. It took at least for me a bit of time to realize the effects of it. Simply because you don't get a huge loads of rewards by one faction.
This is in my opinion one of the best moments of Skyrim and it shows that you can create incredible story telling with several layers even if you don't have a lot of dialog. Sadly it was also one of the very few moments of any of the recent Bethesda games.
Why this matters for Fallout?
Well the reason is simple. Because this should be the core principle for Fallout. Not just this Fallout. But any Fallout game by Bethesda. What should matter is the motivation of characters and not if outcomes are clearly good or clearly evil. I am not saying that every quest and every NPCs has to follow that. It would be silly of course. There can be psychopaths and there can be also your typical goody goody two shoes. But most situations should be rather subtle in their effects. And that can be even done with very evil or very good characters. As long as the organizations you work for have proper motivations that sound - from their position - reasonable. I never felt like any NPC ever did that in Fallout 3.
The reason why this works so well is because it feels believable. We can relate to it. Not everyone for the same reasons of course. Some will always feel stronger with a certain faction. But as far as Fallout goes you should avoid factions that feel like obvious psychopaths killing everything in sight.
That is why Paarthurnax and the quest to kill or not to kill him should be a guide line for future Fallout quests in my opinion. Same as how New Vegas treated factions. And I really hope that someone at Bethesda took his time to look back on this and got this kind of quality also in to Fallout 4.