I remember one of the devs posting a while ago that they would not add any more starting dates, is it just players talking about it or was there devs talking about earlier start dates too on this forum
podcat talking about how only 4% of games uses the 1939 bookmark and the tendency of players to use the earliest bookmark, including in other Paradox games.
I usually prefer to go early, except CK2, where the Viking start can be a bit too early at times (and the world ends up drastically ahistorical). EU also has some neat things you can do with later bookmarks. HOI4 does seem to have the mechanics in place where the devs could, conceivably (but with an immense amount of superhuman effort), make a "pick any day in WW2" timer like CK2, EU3 and EU4.
Two of the new people seem programming and AI focused, so I am hoping to see good advances in that area first. Mods can fill in wishful wants but not mechanics and core gameplay.