Heroes 5.5 WarGame Edition - Tactical Edition.

If the mod has an extra ID for a spell and compatibility with other mods that require this ID is not planned, you can make adding a turn an activatable ability.

As I understand it, there are only 4 such spells.
SPELL_ABILITY_CUSTOM1
SPELL_ABILITY_CUSTOM2
SPELL_ABILITY_CUSTOM3
SPELL_ABILITY_CUSTOM4
However, for each specific class, you can customize its effect and its application conditions.
By the way, an idea for the Orcs - to receive useful bonuses for sacrificing goblins.
P.S.

by placing production buildings near the enemy

What production buildings can be built near the enemy in Heroes?