In Heroes V, the “Battle Machines” skill is not a priority; moreover, it is rarely developed, with players preferring to focus on developing luck, attack, defense, magic, and so on. This skill is essentially weak compared to others.
Question: Is it possible to enhance it in such a way that it would be interesting to develop?

I know of at least two mods that affect battle machines:

1 - LBE - minimal changes towards balance for HeroesV 3.1 
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Changes to battle machines:
- The base number of hit points for ballista has been reduced by half;
- The base number of hit points for the tent has been increased by half;

2- UNIT - Creature Balance + visual changes
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The author of this mod significantly enhanced battle machines, specifically:

-Ballista. Base price: 2000. Increased bonus to damage and health depending on the hero's characteristics and the level of the "Battle Machines" skill, as well as an increase in their base value.
-First Aid Tent. Base price: 1500.
Now, the number of uses of the "Healing"/"Plague Tent" ability is 10 times.
Increased bonus to health depending on the hero's characteristics and the level of the "Battle Machines" skill, as well as an increase in the base health value.
-Ammunition Cart. Base price: 1000.
Increased bonus to health depending on the hero's characteristics and the level of the "Battle Machines" skill, as well as an increase in the base health value.