I have released several mods that have touched upon the Main Quest in the past. Some of them added little immersive details, others added dozens of new quests or new choices to make. Since it is a problem for people to have many .esp-s activated, I decided to merge them all together, and release them as one big overhaul. Similarly to the individual mods, this one should also be clean, bug-free, and compatible with Julan, Ashlander Companion, and Morrowind Rebirth (which is not a Main Quest mod, but I always get this question anyway). The mod is NOT compatible with Great House Dagoth and similar "joinable Sixth House" mods, because this mod already covers this feature - in my own interpretation of such an event.

List of mods that have been combined into this one, and their features:
(Download links for the individual mods are below their descriptions, if you prefer to only have some of the features.)

Living with Caius by OperatorJack: This mod alters Caius Cosades' home in Balmora to be slightly bigger, have a second floor, have a private patio, and have a spare room for the player to live in if they decided to help Caius by joining the Blades. The spare bedroom is locked, but you can get a key from Caius when you accept his offer to join the Blades.

https://www.nexusmods.com/morrowind/mods/47898?tab=description

Refuse the Main Quest: Are you truly a 'freelancer' adventurer? Or your current character is not actually the one foretold in the Nerevarine prohecy? After you deliver and give the package to Caius Cosades, you will have the opportunity to tell him that you do not want to join the Blades. You will be free to explore Vvardenfell on your own without any obligations. No more burdensome reminders in your quest log. Nothing. Be prepared though: you know somebody who is a member of the Blades, the intelligence agency of the Emperor. There will be consequences of turning your back on them.

https://www.nexusmods.com/morrowind/mods/44802

Nationalist Nerevarine: Have you ever wanted to roleplay a Dunmer nationalist who takes no orders from the mongrel dogs of the Empire? But the Main Quest still bullied you into being a Blades agent? Inspired by the traditions of role playing games, now there are two paths to complete the Main Quest. One of them is the regular one, being an Imperial agent. The other one is to take the package in the first quest to a rival (vanilla, and lore friendly) faction, and work for them. To begin, when you exit the Census and Excise Office in Seyda Neen, talk to the Dunmer standing there.

https://www.nexusmods.com/morrowind/mods/45687

Imperialist Nerevarine: Are you a loyal servant of the Empire who doesn't want to contaminate his/her character page by joining the factions of the savage natives that our Empire has subjugated? This simple mod provides you an opportunity to either accept or reject Sul-Matuul's offer to adopt you into his tribe upon completing his initiation rite. Now you can finally role play an Imperial character, who only joins factions like the Legion, and they won't be bullied into a faction hostile to the Empire by the Main Quest.

https://www.nexusmods.com/morrowind/mods/45815

Hortator: This small mod adds the "Hortator" faction to your character sheet, with you being at the rank of "Hortator," once all three Great Houses named you as such. I just felt that it is strange that every other rank you achieve in any faction is acknowledged on your character sheet, no matter how insignificant it is, while being the wartime leader of Morrowind isn't.

https://www.nexusmods.com/morrowind/mods/46856

Ashlander Quests: Allows the player to do 11 more quests for the Ashlander tribes. They are little, roleplaying quests which help you feel more immersed with the Ashlander way of life: Help set up the ebony trade, hunt down dangerous beasts, help an Ashlander learn more about the outside world etc.This mod might be ideal for an Ashlander warrior roleplay, or for roleplaying a Nerevarine who actually cares for his people so he helps them out.

https://www.nexusmods.com/morrowind/mods/46817

Consequences for Looting the Andrano Tomb: There will be visible consequences for looting the Andrano Ancestral Tomb as part of the Main Quest now. The Dunmer consider their ancestors to be sacred, and any violation of them is a grave sin (pun intended) in their eyes, especially necromancy and tomb raiding. Therefore, this mod aims to make your deed actually look like a huge religious and political scandal that affects the life of the people of Vvardenfell and makes your next playthrough of the Main Quest a bit more immersive.

https://www.nexusmods.com/morrowind/mods/49728?tab=description

Exterminate all the Brutes: Adds a new quest for exterminating the entire Sixth House faction. To begin: Finish the Main Quest, and talk with Lord Vivec about the topic "much to do," and advance through the topic "must be hunted down and destroyed." You will be directed to Ralyn Othravel at Ghostgate, Tower of Dawn, who will give you the tasks one by one about exterminating the Sixth House. 

https://www.nexusmods.com/morrowind/mods/49322?tab=description

Joinable Sixth House - So to Speak: With this mod, you can join the Sixth House! So to speak. While I have nothing against the other "joinable Sixth House" mods out there, I believe that my interpretation of such a scenario is more believable. Without any spoilers, please note the "so to speak" addition in the mod's name. You might get disappointed if you expect some grandiose plot in which you become a living god. Let's just say that this is more like an additional, optional quest in the Main Quest.

https://www.nexusmods.com/morrowind/mods/49778?tab=description

Past Life Regressions: Throughout the game, you receive visions of your previous life as Nerevar or as one of the failed incarnates (Ane Teria, Conoon Chodala, Erur-Dan, Hort Ledd, Idrenie Nerothan, Peakstar). The visions are triggered by visiting certain locations.

https://www.nexusmods.com/morrowind/mods/49315?tab=description

Sixth House Smugglers:  Adds Sixth House smugglers to some smuggler caves, and a non-journal quest to hunt them all down.

https://www.nexusmods.com/morrowind/mods/47602?tab=description

Vampire Nerevarine: Removes all the obstacles from becoming the Nerevarine as a vampire, and provides a lore-friendlyish explanation for it. Complete Azura's Quest with a vampire character, and Azura will teleport you inside the Cavern of the Incarnate, and you'll get a journal entry about what happened. (Your character will speculate that Azura had a reason for doing this with them.) If you complete it with a mortal character, everything would just work normally, like in vanilla. (You won't get teleported, and you won't get a journal entry.)

https://www.nexusmods.com/morrowind/mods/48290?tab=description

Some bonus features:

- Your status as "Nerevarine" will be listed in your character page upon touching the Moon and Star
- In the Cavern of the Incarnate, Conoon Chodala will retell you his story from The Elder Scrolls Online

Requirements:

Morrowind, Tribunal, Bloodmoon.