I haven't played it myself because of its incompatibilities with other mods in my load order, but Dragon Captions - The Elder Council is apparently a mod that lets you earn "nobility points" and rise to become Duke of Colovia.
Aye. TEC does indeed eventually allow one to become Duke of Colovia. (I should point out that I use the non "DC" version.) It seems a more or less honorary position. It does, however entitle you to a seat on the Elder Council and quarters in the Imperial Palace. A shame about the incompatibilities. I'd like to give Weather: All Natural and Immersive Interiors (especially the latter) a try. Sadly, All Natural recommends not using TEC. As I consider TEC the very core of my installation it wins out in any conflict.
I believe Kvatch Aftermath, from the same author as TEC, allows one to become Count of Kvatch. But if you are already happy with Kvatch Rebuild, which also offers this options, there is no great reason to switch. (I use a third option, Kvatch Rising, which does NOT offer a noble title.)
-Decrepit-