So in a few days I'm planning to get the Elder Scrolls Anthology (I've only halfheartedly completed Oblivion and completed Skyrim) and I've meticulously planned my characters, so I just want to check with people who've played the games to see if there are any factors I'm missing (as well as any major notes on my character builds. Thank you so much to anyone who contributes to my Elder Scrolls experience in any way!

A lot of the factors I would like help in noting are things like guilds/organizations with extensive quests, daedric quests that would be appealing to each race/class, vampire clans, any major choices in the plot or the game (killing paarthunax or vivec, e.t.c.), really important universal things (like the levitate spell and the Boots of Blinding Speed in Morrowind), and fundamental things I may have missed (for example, do you pick a Birthsign in Daggerfall?).

So throughout the games I'm trying to build sets that incorporate the stereotypes of each race so

Altmer-Destruction mage

Argonian-Stealthy assassin

Bosmer-Archer

Breton-Alternative magic (not using destruction)

Dunmer-Combination of combat and magic

Imperial-Using blades and other basic combat staples

Khajiit-Stealthy assassin (occasionally using magic)

Nord-Alternative brute force melee fighter

Orc-Brute force melee fighter

Redguard-Skilled and tactical melee fighter (sword and shield, basic things)

Arena: From what I could tell the only thing you choose here is your class (and you don't customize it?)

Altmer-Battle Mage

Argonian-Assassin

Bosmer-Archer

Breton-Nightblade

Dunmer-Spellsword

Khajiit-Rogue

Nord-Barbarian

Redguard-Knight

Daggerfall: My goal here was to net a -12 score (from the special advantages/disadvantages) because I've heard that that's the cap for making leveling easier. I commonly use basic skills like the personality skills(mercantile, etiquette, streetwise), the athletic skills (running, jumping, e.t.c.) because I eventually ran out of relevant skills to the character build.

Morrowind: So I tried to add a lot of Marksman skills in here so more characters were capable of ranged attack. Also, if someone could clarify this: for the reputation granted by your position in another faction (telvanni rep dropping because you're in the mages guild), can/how can you fix this and be in both/all of the groups?

Oblivion: So a lot of the characters have personality skills (mercantile, speechcraft, e.t.c.) due to the fact that I ran out of relevant skills (ideas for replacements are welcome)

Skyrim: Since you don't have any major skills and all the skills govern leveling capability, I decided to just focus on 7 skills and then reset them to 15 to avoid having to switch my focuses.

Okay so that's it, please let me know about ANY thoughts you have on my builds, my factors for roleplaying, anything! Thank you so much!

It doesn't need "fixing" as it works just fine in the game.
The disposition changes are not very drastic, so for the most part you can ignore them.
Yes, you can join both Telvanni and Mages Guild.

This helps you plan your character before you jump in game: http://morrowind.inventivegamer.com/tools/chargen/

Since this is your first time playing MW, I wouldn't stress too hard about your build. Just get in the game and enjoy it.

And in case you haven't seen this: http://www.uesp.net/wiki/Differences_Between_Morrowind,_Oblivion,_and_Skyrim

Killing Vivec doesn't finish the MQ.

I suggest playing Morrowind without mods first, so you can experience the original game.
Although I do recommend the two community patches, to fix many problems. You can learn about them http://www.gamesas.com/topic/1305729-mod-recommendations-for-new-players/ under the "essentials" header.

I agree with Pluto: I think this does not need "fixing." If I were put in charge of making these games I would add more. Faction reputation is one of Morrowind's better features. I think there wasn't enough of it, even in Morrowind. And I'm sad that it was removed altogether in Oblivion and Skyrim.

Here is my opinion: I think it is best not to approach Elder Scrolls games with a do-everything-on-one-character attitude. Personally I think this cheapens the experience of playing the games. I realize that the later games encourage this mindset, but that does not mean that we have to give in to it.

Going by Morrowind, Bretons are famous for their sorcerers, so 'alternative magic' isn't really a thing among them.

The way I understood it is "alternative magic = all magic, except for destruction".