#1. I don't think we will get DDs on minor/aspiring powers. The game looks to be in an advanced state as it is, we have plenty weeks to go, of course, but some of the big nations and major mechanics were not covered by DDs so far. So I doubt we will get to the point where they need to tell us the details of such nations.
#2. Poland and Romania were mentioned during livestreams, playthroughs and we kind of know that their role is significant enough. Should add Yugoslavia to the list, but I don't remember reading or hearing anything specific about them.
#3. These nations don't really need individualised focus trees, their goals were quite similar and faced pretty similar political dilemmas. But their individualisation would make them more interesting to play as, I guess.
My hope and speculation from the information we have so far is that the role of such countries is influenced by the resources and factories recreated in the game to some degree. For example, the role of Romania as an oil supplier for Germany is quite neglected in HoI3, in fact, it barely has enough for it's own motorised campaigns if you choose to produce such units. Other small things can impact gameplay: for example, Romania's dependency on fabrication patents or imports from external partners, especially from the Skoda factories is not coverable in HoI3 (except maybe for the names of equipment units were assigned, which was a very nice touch). I'm curious if that can change in HoI4, especially because brands play a bigger role this time around. The Skoda factories "change in management" in 1939 is an interesting turning point for Romania, as its army was depending on imports from there and the government failed to sign any deals with France or Britain to provide its army with ANY alternatives. That one event, an external one at that, narrowed down the political alternatives from that point forward - for a game, such scenarios can create emergent gameplay if exploited properly. Now if it were possible to add such options to diplomatic deals, a small country can develop some tech that would make its factories a regional supplier, an alternative and a new strategic POI in the game. So small things like that can have a really juicy impact on gameplay and we've seen minor hints of that (for bigger nations so far, going for one Germany manufacturer rather than another for producing tanks) and we've seen hints that Romania is a natural choice for oil trading. It would be nice if smaller countries can influence the game because of the addition of any such feature and if this can exploited strategically, that would be awesome for gameplay, even if you don't actually play as one of these countries.
Another interesting aspect Paradox can introduce about these aspiring nations is in the pacts they can make with each other. A central-european alliance can create some interesting game dynamics, what if they choose to help each other by defending Czechoslovakia in 1938, without the help of Great Britain and France?
