Need suggestions on a grand strategy combat system

I am currently creating a grand strategy game similar to games such as Total War and Crusader Kings. I wanted to create a Total War style combat system in which the players controls representations of their units, when the players battles, they fight on a separate map with those units. [Example Below]

However, I feel like the only way this would work is if it was turn-based but this risks player engagement, having to wait for other players battles. If it wasn’t turn-based then if the player is already in a war and another player attacks them they’d have to fight on two different maps which will just be confusing. A simple fix is using a unit v unit combat system like Crusader Kings [See Below] but I feel this puts less focus on actual war strategy and more on territory.

Crusader kings 2 military - photographyvica

Any suggestions/ideas on how to achieve this more effectively would be greatly appreciated. Also happy to hear any ideas in general.