I would like to see tripmines in the game. In some games, you can set many tripmines, even on top of each other, and they can cause a huge amount of damage when tripped. This does take time, and they don't last very long (in the minutes). These are buried, and cannot be seen without a scanner. Trip mines can sometimes be tripped with weapons fire.
I would also like to see something like caltrops, where crossing them incurs a penalty, like movement, etc. These could be EWAR type penalties, based on the chemicals used to create them. Basic model slows movement and causes light damage. Caltrops are visible obstructions on top of the ground. Caltrops cannot be removed, they have to decay.
In real war terms, mines were carried and set by almost any kind of vessel. Special minelayers did exist, but almost any PT boat, submarine, warship, even plane, could drop mines. It did require a special minesweeper to remove them.
I would propose that light bots, and even industrial bots, be able to set mines and caltrops. This requires a special minelayer attachment that is similar to miner or harvester equipment. A specialized minelayer bot could be X amount better, and lay better mines. Mines can be detected with scanners, and neutralized with minesweepers or weapons fire.
So, what's the schedule?
edit: I would not be in favor of permanent static mines.