Not every player is into exploring dialog options, just as not every player is into combat. The various guilds, factions, and cliques should each have missions and methods that cater to different styles of play. A political faction probably isn't going to want you to stroll through the front door of the rival faction's meetingplace and start chopping heads.....not that they'd be sorry to see it, but it would make for some rather bad publicity. Your mission profile would more likely involve convincing, intimidating, or bribing a particular member of that group into doing what your faction wants. There should be missions that can only be solved with dialog, others which require stealth skills, and yet others which are inherently violent.
Not every character should be able to even begin every factions' quest lines at low level, even if they can probably do so eventually with enough character advancement. A few minimum requirements would make a tremendous amount of sense, so you don't have an illiterate barbarian as head of the Mages Guild, or a thief as the Champion of the Arena, unless they can do so by actually developing the required talents, thereby becoming a hybrid class that can do both.
I'd like to see more done with food, drink, and sleep. Making it a requirement for survival would annoy a lot of players who just want to run around and kill things, so it would need to be implemented as a long-duration "minor penalty" or "minor perk", not short-term "healing potions", as food was used in FO3.
BTW - for the poster who assumed that MW's dialog was similar to OB's:
Not at all! MW had about 3-10 times the dialog that OB did. At first, the topics were fairly limited, and you could only select topics on a few things: their basic background, advice, secrets, lore, occasionally about occupation or faction matters, and generally one or two other items of local concern. By the time you got well into the main quest, had finished a few minor quests, and had travelled to most of the major towns, the list of topics had probably grown considerably. A few NPCs, such as Savants and Scouts, might have 10-20 topics from the start, and that would grow rapidly as you "unlocked" further details by activating the root topic. Essentially, you could (and had to) scroll through pages of topic choices. Compare that to OB's 3-4 dialog options per NPC, on average.
I think that more diversified challenges must go, as you propose, with the ability to take really different ways to handle the game, the main quest, and the factions... The point is not to ask everybody to deal with all challenges who ever is his character, but to have his character face the challenges corresponding to his role. That is a lot of work indeed. Oblivion only gave one path/solution/role through the main quest, and most factions et secondary questlines were centered around combat. The idealist idea behind this thread is that oblivion should have had 4-5 time more dialog lines/topics and quests, so we could have played really different adventures (in oblivion, your only possible adventure was combat).
For dialogs, I would like something a bit more emotional with more consequences, than MW system. I really love a game like the witcher where you can completely turn an NPC against you or where you have to take a side during an enforced dialog. It pushes the player into a real RPG challenge : mixing what his character should do based on the role and what is the best to overcome the problem. Moreover, you never have all the answers and cards in hand when you have to decide. There are always some shadows left so you are never sure to have choosed the best... and off course, you rarely discover immediately if you did right or not, making the reload-retry exploit not that easy.