My suggestions:
*Tamriel --> Akavir or Akavir --> Tamriel invasions? I would like to play bookmark of Mr.Uriel V. Septim and fight against races of Akavir.
*Creation of Skyrim --> You need Amulet of Kings for the Tamrielic Empire so to create Skyrim or Nordic Empire you should have Jagged Crown no?
*Creation of better portraits for Redguards --> Because African portraits don't looks like pure Redguard. Redguards are little bit more white no? (Before you start to write dumb comments: Im not racist!)
*Artifacts --> I would suggest new system for artifacts (maybe something like valyrian swords in GoT mod) so when you battling someone there's higher chance to stay alive when losing when you have good weapon or armor or maybe you would like something like this: Characters can buy some normal artifacts and equip them.
*Lunatics --> I have crazy suggestion. When you have lunatic trait you will have option to convert on Sheagorath religion.
*Elder Council? --> Game would be more intresting when Elder Council will be in game. They should changing and voting for new laws and sometime maybe some ambitious Imperial Battlemage would try to usurp Tamrielic empire (Heh! You know what i mean

)
*East Empire Company --> I know it exist ingame but it should have some flavour! It should be supported by Empire and Emperor can donate them and East Empire Company can pay you taxes or give you from time to time some artifacts when you'll have good relationship with them.
*Imperial Legion --> Should be under control of the Empire and have HQ in all capital cities of Tamriel provinces. When the Elder Council try to install the new Emperor they should bribe the Legion to join their revolt. Too when some province fight against the Empire the Legion can choose: To join rebellion or to support Empire
EDIT(1):
*Tamriel vs Dominion --> When Tamriel is created and holding Summerset Isles there should be huge revolt for restoring the Dominion and after restoring there should be special CB to attack Tamriel, install Tamriel as vassal puppet and convert religion
*Interregnum factions --> There should be added to some special bookmark and each one of them fighting each other to control Cyrodiil and to control other 2 factions (It would be grat if we can have such epic wars of factions)
*Guilds --> I know they are in game but tons of flavour can be added. Your character as young can join this guild (Mages, Fighters, Thieves...) and learn (I saw something like that on earlier versions of EK because my son get Mages Guild member trait or something like that) (Mages-->Learning) (Fighters-->Martial) (Thieves-->Intrigue) after some yoears of study they can complete it and be fully member of this guilds also when they are members there should be CB for taking Guildmaster title and after winning war you can establish some HQ for this guild.
*Special Guild --> Something as Dawnguard when they become members they will hate vampires (-100) and can have special CB to attack any vampire rulers.
*Mages --> They can learn some special languages (Daedric, Dragon...) and speak with them (There should be event chain to this)
EDIT(2):
*Daedra invasion of Tamriel --> When there's no emperor or at least someone who wields Amulet of Kings there should be possibility of daedra invasion to Tamriel. Because it happened on Interregnum it's lore friendly and a good feature.
*Challenging to duel --> From Skyrim we know that one Nord can challenge the other to show who is stronger or to usurp power. My suggestion is that you can make event chain for this duel. The keyrole will have weapons, armors and too traits (dragonborn, brave, thu'um...) and martial. When you'll win you can choose: To give mercy to defeated (usurp or vassalize his main title) or to slain him (giving -100 opinion to members of the family) when you choose to give him mercy he can accept his defeat and be your vassal or he will want to be slained after duel (this will give 200 prestige to defeated before he dies) then the victorious can choose: slain him (-100 opinion of his family) or let him alive (-200 prestige). When you lose you can ask for mercy (-200 prestige) or to die with a sword in your hand (200 prestige before death).
That's all i can suggest for now. Also i apologize if i stole someone's idea because im too lazy to read those comments

and i apologize too for my grammar because i don't have time for grammar correction when there is holiday. Also when i'll get some other ideas i'll edit this comment and add them here.