Controllable heros
Unfortunately we cannot disclose this yet, since the map is being made and hence subject to change. Of course, most of the characters you mentioned will appear in the next chapter, but whether any of them will be controllable by the player at some point of the map cannot be confirmed yet.
Note that the current pattern with the scenarios has been that in each scenario there are two new controllable heros. Whether we continue to do so with Chapter 4, I cannot disclose at this point. But even if we would continue the pattern, the old characters may also appear later in game as additional heros. But no promise.