Just got back from playing Germany as Black ICE, and one of the things I really liked about it was how many more things you could do -- build massive buildings such as a giant ministry of finance building that gave you a higher income, mechanize your farming (give tractors to every farmer), expand mines, build more efficient highways, etc. Many of these cost a lot and/or have penalties to balance them, so you have to put some thought into which ones to go for. For example, the Palace of the People gives +20% ruling party support, but -10% money.
I don't want HOI4 to be a Black ICE 2, of course, but all the decisions and events really do add a lot of flavour to what would otherwise be an uneventful pre-war build-up.