What should be added to the top five from the previous installments?

1) Really?
2)....
3) We need new creatures, I agree. Many are missing from previous installments.
4) Resistance spells from different schools of magic, like in Heroes 4: Order's Aegis, Death's Aegis, Chaos's Aegis, etc.
5) We need new cities! Swamp and the Nighon (Dungeon from Heroes 3) would be great.

Now, explain to me, how would you combine Nighon and Dungeon? They fight over power in the Dungeon and for the liberation of minotaurs from the slavery of the elves. Too many races will negatively affect the game's balance. Swamp could work, but Nighon only if you think about it very carefully... Of course, the idea of two races in the Dungeon is cool, but I don't know how you would handle the troops and the hero characteristics.

Added after 41 seconds
2DrNik, take a closer look; these spells definitely affect the movement range.