I would add taverns to the top 5, the ones that aren't in castles (they were in Heroes of Might and Magic IV). You could send in one hero and buy another (and they could be from any race, not just two to choose from, as in the castle). Otherwise, if your main hero is, for example, a demon, you'll only be offered demons. If you're conquering, for example, a Dungeon or Academy castle, it doesn't really make sense to put a demon there. The morale of the troops decreases.
Yes, and in general, there could be more heroes, because the choice isn't very big...
And, as someone recently posted, if your hero is a woman (for example, Ora from the Academy), and she's riding an elephant, it looks like an old man with a beard and a hookah. That doesn't work!