I loved playing as Rizia and Sordland, but having supreme power (unless you go constitutional or reformist) does get old after a little bit. Dont get me wrong, both of the aforementioned play throughs are great, and I intend to return to them, but a play through where you get to act out the decisions of a noble or governor of a local region would be awesome.
Maybe you’d make them have a different culture or religion to their parent state, meaning you can choose to try and go for autonomy, independence or simply having it remain as is. Maybe you can use the lack of having to worry about the entire nation, to focus on your own economics and influence, allowing you to puppeteer the central government and whoever sits at the top. There’s so much you could do with this concept and I feel that lack of worrying about foreign politics and the affairs of your whole country could allow for a play through which is much more based around connections between different people and such.