The prospect of synchronizing global and arena time remains one of the most exciting. However, I have become disillusioned with it.
Imagine:
Two heroes (blue and green) have a falling out, and a small skirmish begins. And it seems that green is starting to gain the upper hand...
But on the next turn, blue receives reinforcements in the form of a garrison from his castle, along with his fellow hero. And now, together, they begin to push back the enemy.
The enemy is having a hard time and cannot expect any help. But then his ally, red, appears, and with cries of "fight, fight!!!" jumps into the fray.
After a couple of turns, the heroes of the other colors join in with fresh forces.
As a result, for half the game, a huge mess is brewing somewhere on the map, and it is even difficult to imagine an interface for managing so many players.
Some of the heroes are already fighting, while others are left without units (!)
In general, complete chaos - like World War II.
I have only seen something similar once - in the game Dungeon Keeper, with the Armageddon spell. At the same time, all the enemy creatures rush to destroy your Keeper's Heart.