What would you change in Heroes of Might and Magic IV?

2). What do you think about making small monsters stronger?

The idea of making small monsters stronger is exactly what's needed! I'm all for it!

Someone has already suggested replacing Nature's "First Strike" with "Ignore First Strike." We haven't had any ideas about Slow or Fatigue yet. I think it would be interesting to expand Fatigue to Slow, reduce the effect (instead of halving the speed, reduce it by -3), and lower it by 1 level.

Regarding the spell replacement, it's a very reasonable idea, and I like it too. However, "Ignore First Strike" is completely useless in some cases (when there are no enemies with "First Strike"), and in others, it's simply incredibly effective (against Dragon Golems, Champions). However, since it's been suggested, it means they've thought about the balance. So, that's okay! :)

Regarding the Barbarians, it has already been suggested to give them 20% resistance from each Castle Absorber. And not only that, there's more detail there.

The link is very interesting, thank you. But will there be any limitations on the bonus from the Absorber, Pit, and Arena? Because if the Barbarian troops' resistance exceeds 50%, it will seriously disrupt the balance. However, this won't affect the game when playing against a human player – a player can't have more than three Barbarian castles in principle, so the resistance will be no more than 49%, which is acceptable.