It would be interesting if they could some how have it so you can win the war for your faction. Not just the Legion or the Stormcloaks. Just like the war for Fall Out New Vegas. You didn't have to win the war for NCR or the Legion. Multiple factions were able to take hold. So what possible factions do you think would be able to do so and what impact do you think it would have. Only possible factions I could think of being able or willing:

Imperials
Stormcloaks
Thalmor
Blades
Dark Brotherhood??

Any others you can think of put them in this section.

Also why does the Jarl of Whiterun have to side with the Imperials. I would say he is one of the better Jarl's yet from time to time I set my character up to side with the Stormcloaks and I would still like to see him be the Jarl. Perhaps a specific quest you could do would set him up to be one or the other.

I have not created this section for people to say "This isn't possible because bla bla." This section is made so people could talk about what they think it would be like if this could happen and what group they would support.

I don't see any faction in Skyrim, except for Imperials/Stormcloaks/Aldmeri Dominion, that could win the war. Neither the DB or the Blades would have the manpower to do so.

Neither would the Thalmor, for that matter, they are just a small diplomatic 'police' force. I would be more interested the Hold's asserting more independence. Why shouldn't Vignar, or Balgruuf be high kind instead?

This a heads up ^

Now the thing on those two groups. The Dark Brotherhood is an extremely large group. I don't see them really wanting to take it but they def have the manpower. They have people spread out in several sanctuary's in several countries. Now for the Blades. They used to be huge. Now they are a small amount of them left. They have superior battle techniques But they just need a simple push into recruitment.

This is a good idea, Honestly it really is.