Here is a list of the expansions that should be done, we know there will be a couple of them.
1.Taking the Empire
Quick question, what was the common factors in the earlier empires until the death of Martin Spetim? Dragonblood. Therfore I am proposing that the Dragonborn has a major claim to the throne. Not to mention he also has claim to lordship over the dragons, meaning that it wouldn't be hard to deal with the Thalmor if a few hundred dragons worked together to crush the stinking elves.
The plot line would go somethign like this, civil war quests end, main quest ends, and then the thalmor decide to attack the dragons at the throat of the world. The Greybeards wipe the floor with the Thalmor attack squadron with only their voices, and you meet with the dragons about a retalitation.
You then carry the news to the blades, even if Parthunax is still alive, and they agree to aid you in the fight. They also tip you off to the location of a old magguffin that would allow you to shout without as much of a wait. You then go dive through a even bigger dungeon than any other, and recover it.
You then wind up just outside of the imperial city's gates with the Emperor(or head of the Elder Council if you did the Dark Brotherhood quests) speaking to you. You will quite simply state that you intend to destroy the Thalmor, and have the means to do so(Either the Stormcloaks of the Leigon members that used to be in Skyrim on top of a thunder of dragons). The Emperor(or head of the council) will then quite simply refuse, and you will have the option to either let him live and return to the city, or to shout him down.
Regardless, you will then have to siege a expanded version of the Imperial City(few additions have been made in the last two hundred years) and you eventually stop before the Statue of Akatosh(remember the end of Oblivion?) and find the remains of the Amulet of Kings beneath the statue. You will then grab the Amulet(which for some reason nobody could pick up for several years) and wear its remains as you march on into the White-Gold tower. You then have a face off with the Thalmor ambasador, and wipe the floor with him. You will then talk to the Emperor if he is still alive, and he then sees that you wear the remains of the amulet and decides to grant you the throne in his stead(If its the head of the council he just declares you emperor). If you killed him, you just claim the throne.
You then get to join several more instanced battles as you get closer to the Thalmor capital on the isles, and come face to face with the leader of the Thalmor, and face him in single combat to the death. You will defeat him, and the Thalmor will rejoin the Empire, making you now the ruler over Tamriel.
What do you think?