Im doing a multiplayer realtime-strategy similar to total war, without the 3d battles. Also the entire game is realtime and more streamlined for faster multiplayer.
You build cities and develop them "on the map" and train armies. When armies meet the "map-game" continues during the battle which takes ca 30 sec.
Battles are realtime and you decide which unit of some choices will be sent to each "slot" on the field (units dont move around).
If a unit dies you choose which one to replace it in that slot (both melee and ranged slots exists).
During battle, only the player involved in it are "locked" into controlling the battle, other players go on as normal.
If another battle is triggered but one of the players involved are already locked in another battle, the new battle will be resolved once player is available (the two armies will be locked while waiting).
Would this work you think? Battles will not be super frequent. Maybe you can "leave one of your battles on autopilot" although part of the fun is resolving the battles...