This suggestion is probably too late in the day, but perhaps you can consider for DLCs etc.

Characters add a lot to immersion. It feels so much more authentic to see planets run by governors, fleets commanded by admirals and so on, as opposed to "magic". Adds the "human" (or equivalent) element, so to speak.  Yet it is something usually neglected in strategy games (except a handful of games like Crusader Kings, Romance of the Three Kingdoms etc).

The Heroes system, as I read in the DD, is interesting, but is still woefully limited and "gamey". I am happy to accept heroes from "The Academy" as "special characters" comparable to Maesters from Game of Thrones or the Bene Gesserit in Dune. But it will be great if there are other "normal" characters in the game- 

1. They will be have names, portraits and stats randomised. They will be both good and bad (i.e. just normal people - some strong, some weaklings, but generally weaker than the Heroes).

2. They will be strictly limited to your empire's (or equivalent) constituent species. They are just citizens coming up through the ranks along the normal hierarchy of the empire.

3. They will grow over time in skills, but along a gentler curve compared to Heroes.

4. In the absence of Heroes from the Academy, these characters will be automatically elected to lead your armies and navies, govern your planets, research, politick, engage in diplomacy etc. Their capabilities will modify how well those actions are performed. The player will be able to observe and (optionally) manipulate them as much as the faction politics allow the ruler. The ruler can also replace them with the much more powerful Heroes as required.

Personally this will make a huge difference as far as immersion / realism (mechanical) is concerned, at least for me. It will set ES2 apart from the masses of generic 4x games out there. The only 4x game that has tried something similar is a little game called Pocket Space Empire, but it does not have the sophistication and possibilities ES2 can bring to this feature.