You choose to fight for the Empire to maintain Skyrim and all it's minerals as they're better equipped to deal with the Thalmor than the stormcloaks. Then you murder the emporer.

Unless you're role playing a Thalmor agent this seems to make no sense whatsoever.

Your Dark Brotherhood. You just kill whoever they tell you to kill (for profit).

You could believe the Empire s the best thing for Skyrim, but not necessarily with Mede as Emporer. Or if you have contacts within the Elder Council...imagine what influence the Dark Brotherhood could have. Most importantly though:

As Sithis and the Night Mother demands.