Sandcastles
Sandcastles are structures in free play mode that can house resources to random encounters. A sandcastle has a bunch of hapless morsels in it, a tunnel leading to hermit crab bloodthirsty funnel web spiders, pony dolls, candy bars, a tunnel that leads to 2 fossilized queens of an extinct species persevered in amber, some old legos, a season pass code, etc. Maybe there could be easter eggs and achievements like say a sandcastle holds a Gameboy with a solar charger accessory if you wait a day and go back to it your ants will use the Gameboy and will start to play with it. Another could be the amber queens and say you release the nearby bombarder beetle and you make him blow holes in the amber, that will release the 1 million-year-old queens and they will walk out and fly off when you defeat the bombarder beetle and you get the Now Off the Extinction List achievement. Sandcastles aren't easy things to conquer because your gonna need a lot of ant power to bring down it because of its huge health pool, it will tell and damaged it is because it looks more and more damaged the lower its health pool.Snipers and Acid appliers
The snipers are another type of formic acid firing that goes for long-ranged attacks and does high damage, you target the enemy by right-clicking them but they have a 30s cooldown. (Actually, this is off topic but can you make all units be able to target something, please?) Snipers are not good at close range because of the previously stated 30s cooldown and that they often shoot over the target when they're close, you shouldn't make most of your army them. Acid appliers apply acid to a large insect's joints say a tiger beetle and will hurt them and cripple their movement, they are not good against small and large in numbers threats though. Decorations and defenses
Have you ever thought your nest feels plain and bland and needs something to make it look good? Well, you can use decorations like leaves and grinded up wood to make your base look natural. You simply place them on the floor and sometimes the walls. These are primarily used to decorate your nest and are only accessible in free play and the formicarium. Some I thought of are leaves, palm leaves, cotton, clovers, spider web, aphid plant leaves, small rocks grinded up wood, sesame seeds, etc. You will have to acquire these by killing or collecting something like say you have to kill a funnel web for spider web or find search the beach for human trash to find cotton.