I have a feeling the OP doesn't know what a guild is....You guys should look it up before labeling everything a guild. Anywho..lets look at these and see if they're adequate, knee-jerk, or make sense.
Bards guild: So....go around, sing songs and play instruments? I don't see how this needs to be a guild, but going to taverns and play some some hot strings, a wicket drum beat, or a powerful wind instrument would be nice.
Rangers/Hunters guild: What would be the purpose of this? Personally, I see not much for this, as it sounds more like a gun club of sorts, or a bunch of big game hunters. I guess that could work if it was an organization of big game hunters, roaming the land hunting large and dangerous game.
Necromancers guild: No, and I'll quote myself why I think it's a bad idea.
Why did I say this? It's very simple, I'm sick of people desiring an organization based solely on necromancy, as opposed to it being sanctioned by a legitimate magical organization. Furthermore, I can guarantee that the "Necromancy Guild" (which is silly in the first place, please look up the world guild already!) will be turned into an organization based on practitioners who are nothing but stupid evil and puppy kickers, and will inevitably try to destroy the new version of the mages guild. Frankly, I find that to be INCREDIBLY boring, stupid, and highly predictable.
Necromancy doesn't automatically make a person evil, it's only a tool like all other forms of magic. It only has more taboo because, the practitioners play around with dead bodies, which upsets certain cultures. Also to note, necromancy as a whole, during the Septim empire, was legal (save for MW, but that's a different issue). Hell, nobles and monarchs would sponsor necromancers, not only to most likely keep them on some leash, but also to curtail bandits and criminals. In addition, the Septim empire sponsored necromancers, and often donated fresh corpses of bandits to them, which they liked because they were often young and strong.
As such, make it a legitimate school of practice, instead of a bunch of puppy kicking, stupid evil guys in some weird cult. And no, there doesn't need to be this [NUMMIT] stupid necromancy hunters again, known as the Mages Guild. That was...ugh, it made me want to completely destroy the Mages Guild and Mannimarco.
[NUMMIT]! There isn't even a Mages Guild! It fell when the empire fell, and two magical organizations popped out from it, the Synod and The College of Whispers. And even if there was a Mages Guild in Skyrim, I do not see why they would have to follow a rule 200 years ago, made by a archmagister who singlehandedly caused half of his council to resign as soon as he became archmage, then got himself killed by pissing off half the guild, and forcing many who left into a life of isolation and persecution.
All of the Oblivion guilds: I'd like it if the Mages Guild was dashed out and replaced by the Synod and College of Whispers, Dark Brotherhood needs to be in (hell, they originated in Skyrim), I hope the Fighters Guild is in (but with a new name and under new management. These guys are mercs, not paragons of virtue!), and the Thieves Guild needs to be like the Thieves Guild in the Illiac Bay area (read the DF quests).
All of the guilds we've seen in TES so far: No. Nearly half the organizations in Morrowind are Morrowind only. Let the nords have their own flavor, have organizations dedicated to the nordic gods (ESPECIALLY Shor).
Morag Tong: I'm going to quote myself again why I am against that
I don't see the point in trying to bring as much of Morrowind as possible to a place that has 1 dunmer village, and maybe a population that's going to have the highest minority race (the majority being nords, duh, at least at 50%). I get it, Morrowind explored the dunmer's culture and life the best. Can we, for the love of Nurgle and Khorne, let another race have the spot light? Plus, I don't see the reason for having 2 of the 3 on the list, and the reasons why below.
Morag Tong: As much as many of you wish, these guys are not 'good assassins.' They're not the common man's assassins or heroes, or anything of that sort; they're chained dogs used only by petty and rich nobles of the Great Houses of Morrowind, and ONLY operated in Morrowind. The only thing that makes them seem 'good' is that they're not psychotic like the Cyrodiilic branch of the Dark Brotherhood. Everywhere else they are nothing more than assassins to be hunted, just like the Dark Brotherhood. The only problem, nobles are more likely to allow the Dark Brotherhood to operate in secret, as they can be bought and used to assassinate rivals, and are completely open to any buyer. The Morag Tong are not. Not to mention, mer breed slowly. Even after 200 years, I doubt the dunmer population would have recovered all that much, and since they're living in the good graces of the nords, having a bunch of assassins would only draw resentment and distrust to them, especially if the Morag Tong could be traced back. This is something they cannot afford.
To clarify, it was the nords of Solstheim, NOT Skyrim, that gave lots of charity to the dunmer in MK's hint. In Skyrim, I would gander to say it was a lot of refugees living in the good graces of the nords. Having the Camonna Tong and Morag Tong would put suspicion and resentment in the minds of the nords, who are not known for being very mer friendly.
In fact, I'd gander to say much of the dunmer culture we knew is pretty much going to change a lot. They're a scattered people, who have been abandoned (likely in their view) by their gods, the daedra and the Tribunal. They live in lands that are nearly a 180 from what they're used to. The fact the nords of Skyrim (not Solstheim, they're a different people) have yet to either kick them out or finish the job speaks how lucky they are, and how much they are being tolerated by the nords. If they began murdering each other and the people who are allowing them to stay, along with having a highly xenophobic gang try to push people around, it would only cause them to be weakened, and bring the hatred and resentment of the nords, who do not need that much pushing to kill off mer.
Oh, forgot to mention the MT is a religious organization. They kill to appease Melphala, and are more religious than the DB. The DB is a much more secular organization, in comparison.
Barbarians guild: What's the point of this? Being a barbarian is not a career, it's a lifestyle.
Dragon hunters guild: That's the Dovakiin, baby.
Witch hunters guild: I'd say change the name of "Witch Hunters Guild" into "The Inquisition" (or something similar). This faction (trust me, it won't be a guild) goes around hunting down Coven Witches, heretics, and daedra worshipers. Some aspects of them will be brutal, some of the newer members doing many unjust and hasty judging, while veteran members (who are still alive) tend to be more even handed and better detectives. I'd say think of The Witch Hunters employed by the temple of Sigmar in Warhammer Fantasy.
Knights/Crusaders guild: Skyrim isn't really a place of knights in shining armor. That's more of a High Rock thing. Joining raiders, sure.
Spies guild: Working as a spie for the Mede empire would be nice.
Ninja guild: No...this sounds like a silly knee-jerk idea. Plus, ninjas are just...well...assassins. Stick with the Dark Brotherhood, only with being a lot more secular (more money, less Sithis).
Pirate guild: Uh huh...this has more water than "Ninja Guild", but I don't see much appeal
Nine Divines/Goodwill guild: I guess the Medes could have allowed the Imperial Cult to try and spread that political move religion, but I'd rather the nordic pantheon be explored in greater detail than the [censored] nine again. I'm sick of the nine!
Political houses (similar to great houses of Morrowind): Expect that to be part of the Civil War stuff
Daedric Cult: I guess
Dwemer (Studiers) guild: Tends to go under the jurisdiction of the magical organizations, who are really the only people that study it. Sure, there are independents, but it tends to be more of a hobby or personal curiosity.
(Imperial) Guard Guild: I doubt it, unless the Mede Empire, somehow, got a hold of Skyrim, but the book makes Skyrim sound like a very unfriendly place for Cyrodiilians to be in.