When I played Skyrim and I played through the storylines of all the different factions on one hand (Thieves' Guild, College of Winterhold, Bards' College, Dark Brotherhood, Blades, Foresworn...) as well as the two main political factions of Empire versus Stormcloaks, I was left with a bit of a void.

I had, and still have, a major urge to redesign the whole political context. I felt that as a leader of all these little factions and with the status I have built up with the Empire in Skyrim that I was probably the most powerful figure in all of Skyrim, definitely since I defeated Alduin, Harkon and Miraak.

So I wish I could merge the Blades and Nightingales, unite all the jarls under one Skyrim, allied to the empire, yet independent so we're not feudal to the Thalmor, I wish I could invest in the College of Winterhold and apply that knowledge to a further extent for my Blades/Nightingales, then make some diplomatic approaches towards the Psijic Order and the Moth priests.

You know... That's how I would fill it in, but in general the gist of it is that I wish I could be able to redesign the political context of Skyrim and its organisations, which would be perfectly logical with the epic status and power that I have obtained as the dragonborn throughout my adventures. A king on the throne of what I perceive to be a perfectly harmonious and strong land.

I've never played all possible factions with one character. So it would never occur to one of my characters to unite opposing political factions. Some of my characters aren't even aware that some of these other factions exist.

Never gonna happen. Nightingales work for personal profit, Blades for patriotic duty (or loyalty to the DB supposedly). Uniting the jarls is just a matter of winning the Civil war for the Imperials. And Skyrim always was semi-autonomous, which is why there is High King in the first place. Don't know what you mean by "feudal to the Thalmor". CoW is already an "Open Research" university. If the Blades or Nightingales want some specific Magic developed, they could arrange for that through the agency of the PC as the Arch-Mage. (But that would also require a game mechanic for new player-created Magic spells and items. Which would require TONS of additional programming.) Communication with the Psijic Order is entirely one-way: They contact whoever; NEVER the other way around. Dealing with the Moth priests, a group based in Cyrodiil, would probably bring the Synod into the picture, and the Synod has demonstrated that it views the CoW as a collection of half-educated hicks and twits.