Annexation mechanic

I think that there should be a feature in which you can pay a small amount of resources to annex a province/city. It would eliminate the stripes from the territory and it would be listed as a core province/city for the country. Also I think that they should make it so that if a captured province is not annexed then you cant build economic or capital buildings until you annex it. One other thing it could do is, make it so that there is a less chance of a revolt in that province. I think it would just be a nice feature to have.