Possible Expansions, Well, one expansion in particular... Options

[Captain Hammer]

So, since this is Bethesda we're talking about, let's all talk about the number 1 expansion that you want to be included in Skyrim, based on what we know so far.

What do I want? Simple. The Ruby Throne.

I mean, seriously, the way the game is currently presented, the final big-bad will involve some manner of sealing away Alduin (Akatosh/Auri-Eil, based on your pantheon of choice) and saving the world. So, why not build on that, by, say, using your newfound status as Dragonborn God-Binder to do something productive.

Example of Productive Endeavor: Kick-start the Fourth Empire of the Dragonborn. Alessia did it. Reman I Cyrodiil did it. Tiber Septim, the Divine Talos, did it. Why in Oblivion's Infinite Chaos should the next Dragonborn not have a shot at becoming Emperor (or Empress)?

I know, I know, there's a large degree of difficulty in trying to figure out how an Elf would become the ruler of the very human-centric Tamriellic Empire. One Dark Elf Empress was difficult enough, even though she did get the job on account of her husband and minor son. Let's not get into the problems that most of the human races would have with an Argonian or Khajiit as Emperor/Empress. I'm sure there's a way to get around this. Even if it does require adopting an appropriate heir from a human household and/or being adopted into that household, giving other members the claim on the Ruby Throne.

According to the lore, periods of severe civil war always come at the end of an Interregnum. And it is always the forging and renewal of the Tamrielic Empire that ends such strife. Historically, when an individual controlled all of Skyrim, it was either as a supporter and ally of the Cyrodiilic rulers (the line of Ysgramoor in the High Kingship of Skyrim allying with Alessia and the First Empire), or that person was Emperor (both Reman I and Tiber Septim unified Skyrim behind them before they could conquer the rest of Tamriel).

And besides, if you can whistle up a dragon with a careful shout, who could stand against an army with that in its arsenal. It worked great against the Redguard Crowns at Stros M'Kai, and that was some of Tiber's most difficult opposition.

[Captain Hammer]

You're right, this might need to be a new game. Emphasis on might. I'm reserving judgement until I see Skyrim in action.

Still, let us not confuse Nafaalilargus with the dragon you get in TES V: Skyrim. The first was an actual beast, one that could be, as was, killed. Once gone, it wasn't coming back.

In the new game, and based on developer comments, we're talking about the Jills, basically divine spirits that are servants of Alduin, and after you kill one of their number, you learn his True Name, meaning you get to use Thu'um to summon that one to do battle for you. Which means yes, you have one dragon. But you continue to have one dragon.

It could play along like this:

Soldier for the Dovahkiin: "Sire, the dragon is down. It took over 100 battlemages, but they brought it down."
Dovahkiin (Me!): "Eh? Oh, yeah, figured that might happen occasionally. Surprised it took this long, really."
Soldier: "Sire, we've lost our dragon. And now their battlemages are turning fire at our army."
Dovahkiin (Me!): "Easy. They may have underestimated my Power. Check this out."
(Breathes in real deep. Then shouts, in Dragon Tongue): "OY! (Insert Name of Dragon Here)! BACK TO WORK! KILL THOSE BATTLEMAGES! AND THEN TAKE OUT THEIR TOP COMMAND!"
(Said dragon reappears, sort of like recasting a summon spell after ally was destroyed, except it's a giant fire-breathing flyer. It lays into the unsuspecting battlemage corps and turns the tide of battle.)
Dovahkiin (Me!): "There, that should about do it for today. Which province are we 'Re-integrating into the Empire' next week?"

And that's on the low end. If you're gonna be fighting, and stopping, Alduin, I could imagine it going some more like this:

Soldier for the Dovahkiin: "Sire, the dragon is down. It took over 100 battlemages, but they brought it down."
Dovahkiin (Me!): "Eh? Oh, yeah, figured that might happen occasionally. Surprised it took this long, really."
Soldier: "Sire, we've lost our dragon. And now their battlemages are turning fire at our army."
Dovahkiin (Me!): "You're right. They may have underestimated my Power. Time to up the Ante. Check this out!"
(Breathes in real deep. Then shouts, in Dragon Tongue): "OY! ALDUIN! I'LL LET YOU OUT FOR HALF AN HOUR! TAKE OUT THEIR TOP COMMAND! BUT LEAVE THE REST! A GOOD ARMY IS A NICE THING TO TAKE AS PLUNDER!"
(Alduin appears. That's right, a frakkin GOD appears to do battle! A giant, fire-breathing, really hungry god.)
Dovahkiin (Me!): "That should teach them not to F@ck with a Dragonborn. We're so bada$$, we bring gods to a mortal fight. You alright, son?"
Soldier: "I may need a drink, Sire."
Dovahkiin (Me!): Well, we are now a week away before our next 'Re-Integration into the Empire.' Who is next, by the way? Anyways, I believe I could now spare the men a night of drinking and whoring. Have fun. Though, send any of the really good-looking red-headed wenches my way. Service to the Emperor is well rewarded."

Just saying that the bloody Dragonborn deserves a bloody empire. And besides, given the whole Dragon-motif of the Cyrodiils, and the fact that the Dovahkiin bloody well saved Skyrim, getting large-scale support shouldn't be too difficult from those two provinces. And it becomes less of my "group of volunteers" and more like "The Legions of the Dragon!" One indicates possibly a few thousand troops. The other indicates several hundred thousand soldiers, well organized, equipped, and trained for campaigns of reconquest.

I agree that it's one thing to rule Skyrim, and quite another to rule Tamriel. But you build on your success. The Blades in Skyrim under Esbern (or appropriate sucessor if the old mentor dies) form your newly reformed Imperial Order of the Blades. You make the expansion more about diplomacy and tact, strategic engagements and a gathering of support like the Hortator quest in Morrowind, but with the effect of building a Legion like the Allies for Bruma ques in Oblivion. You meet with various nobles, kings, guild leaders, etc., and get their support for your cause. You already have all of Skyrim behind you. Take Cyrodiil next. Use the troops to create a professional, prepared army, defeating political opposition at the head and using the body of support as your own. Build a reverse Hydra, if you will, by eliminating the leadership of your rivals and adding their strength to yours.

When you must engage in combat, engage with a strategy that serves your overall goals. Offer terms to those that submit, quarter to troops that defect, position to those that come ready and willing to adopt your banner. Exterminate those leaders you must, bring down the heads of any organized enemy, scatter to the winds any force of fanatics that oppose you. And when the day ends, know that those you gaze upon today will support you, so that the enemy you face tomorrow has already lost his crown.