Army ants live in bivouac, which is a nest made of their own body, they move at day, camp at night. The game is quite realistic so far, so I don't know how they gonna make it work. Trapjaw ants is more probable, they only need queen model to be playable.
Is it plausable to insert army ants in to the fusca colony though the same way the leafcutter majors have been added following game lore.
Leafcutter majors harvest other insects instead of leaves so surely army ants would get away with not living in a bivouac if part of the fusca colony.
That being said, I'm not sure how the individual gameplay would go as army ants as it would be interesting.
I'm not familiar with how bivouac's interact with the world in real life if attacked at night.
Might be a tough mechanic - maybe a bivouac could "spawn" where the majority of your army ants are at night time. All of your army ants "enter" the bivouac and do not respond to pheromone marker commands during the night.
This could lead to boring gameplay so maybe when army ants are selected the night cycle would have to be halfed/slightly sped up. Or we don't worry about it and we watch the army ants chilling and hope they survive.
So you would need your army ants to gather at a point on the map by sundown to be "safe". If your bivouac spawns in the open you are unable to move your bivouac and your ants could potentially be killed during the night cycle as they go to the bivouac and do not respond to your commands to simulate this.
Potentially when the bivouac is spawned it could create a zone similiar to the other ant's underground area where your ants now rest for the night.
This zone can be invaded by insects and maybe any insect killed inside the bivouac would yield 0 food so again you have to prepare and position yourself correctly or you'll die in the night.
To try offbalance the harshness of losing ants during the night cycle and not gathering any additional food; some balancing may require army ants to carry more food. Whether this bonus is only activated during army ants only games to balance out fusca colonies - it's something to test out if going down this idea path.
This could lead to some really diversified gameplay and some potentially interesting levels.