I think HOI problem (more familiar with 4) is that it feels much more half baked. US Congress is mostly click a few event popups, click a few policy stuff in a menu and see the congress members just flip. It's more shoehorning it into the HOI system.
I think you could make the process fun, but in paradox style games where you need to generalise a system to fit everywhere in the world, it can fall flat.