I've seen threads like this before on other forums and personally love the sort of stuff people come up with.
Here's my thoughts (and I'm overall very happy with the game):
Blades
* The option to tell Delphine off about Paarthurnax. I'd furthermore add the option to smack her down with a dialogue option that reminds her that as the Dragonborn you're the leader and she's not.
* I would also add a Blades questline centered around attacking Thalmor camps and gathering intelligence.
* After the main quest, she and her partner would be much more deferential.
* The option to decorate the Sky Temple.
* The option to make money by sending off your Blades assassins for missions ala Assassins Creed or the Shadow Broke DLC for Mass Effect. You run the risk of losing a Follower, however, if you send them on too risky an assignment.
Companions
* You don't have to become a werewolf to join the Circle. You do, however, have to prove you're on their side by attacking the Silver Hand (proceed to next mission without werewolf bits).
* We'd find a book on the Silver Hand that tells them they're an offshoot of the Vigilants that went Ax Crazy even by their standards and exclusively follows Hircine.
* At higher levels, Aela could become a werewolf and fight alongside you in that form. Ditto the other werewolves.
* You don't get the "fetch the mead" dialogue after you become Harbinger.
College of Winterhold
* After becoming Archmage, all the court wizards have a new dialogue option honoring your status as one.
* You can investigate the Great Collapse and discover it was a natural phenomenon, which convinces the Jarl to be nicer to the Winterhold College.
Main Quest
* It's not long enough. After fighting Alduin in Sovengarde, you would be able to kill him but you'd then see him resurrect and fly off as a much more powerful thing.
* You'd then get a mission to hunt down Dragon Priests and other badies to chase down the new and improved Alduin somewhere else. Then you'd have to solo Alduin or fight him with a single follower.
* While inaccessible before you get your dragon, you'd be able to return on his back at any point via fast travel and eventually to Sovengarde.
* The option to talk to Alduin at one point.
Post-Main Quest
* You will get a new dialogue option from the Jarl of Winterhelm, Tullius, Ulfric, Rikke, and other important NPCs. It wouldn't be everybody but it would be a start.
Gameplay
* Attack from horseback.
* An unarmed skill and perk tree.
* Dictate how far your follower should stay behind.
* The option to turn follower immortality on or off.





