Saw this twitter exchange, might see a post next week detailing some stuff for the first content update.
Basically for those unfamiliar with Paradox's approach with their games when it comes to patches they have hotfix patches and content patches. Content patches are free, sometimes they come out at the same time an expansion DLC comes out, sometimes not. Hotfix patches are typically about bugs fixes only, while content patches are usually balance changes (i.e AI improvements), revamped systems, extensions to systems, UI changes, new small features like mapmodes, etc.
For example, the first content patch for Europa Universalis: IV roughly a month after release to give an idea:
http://www.eu4wiki.com/Patch_1.2
Whole patch history for EU:IV to give an idea of what their process is like over time:
http://www.eu4wiki.com/Patches
One thing I'd like to see regarding UI for example is when upgrading fleets that I get a drop-down list for what design to choose for the upgrade. Say you have two class designs for the same ships with different names, when I click upgrade I want to choose the design. Right now when you click upgrade, it uses directly the name of the design so you have to overwrite the name in the ship designer if you make upgrades to the class.
To be clearer: Say I have destroyer class design "A", I build a fleet of "A". Then I make a new design which is similar to "A" with some upgrades called "B", and I make some fleets of "B". Now later I want to upgrade "A" fleet, but right now I can't make it use "B" class design, it can only use "A" class design. Right now I would have to have modified "A" directly and saved it with the same name. A drop-down list when I click upgrade to choose from would be a good quality of life addition for the UI.