A couple things I've learned playing with mines (Ex-Mil's please chime in!):
- The most feared mines tend to be dual or even triple influence mines requiring multiple trips to detonate/activate. Although more expensive/complex, this feature makes it extremely difficult to sweep them.
- Simple counters are very effective, allowing the mine to activate only after being tripped the 2nd/3rd/Nth time. This lets the scouts pass and the mine attacks the higher value units following them.
- You only need one mine to shut down a harbor! One mine, one explosion, one sunk ship and the entire operation grinds to a halt while the sweepers go to work. Same goes for land mines, you can deny the enemy grid squares of territory with one good mine and a whole bunch of dummies. Mines are a weapon of fear and confusion, the more chaos a mine can create, the better the design.
- You don't want to kill soldiers with mines, you want to incapacitate them. It takes 1-2 soldiers to care for a seriously wounded comrade. Can't beat removing 3 soldiers from action with 1 round.
- You don't want your whole mine field to detonate/activate when 1 mine detects a target. Mines are only effective when their location is not known; once their cover is blown, the enemy just maneuvers to avoid them. Then they call in artillery to "clear" your field. How about a TDX shell designed to detonate 15cm below the ground? That should do a number on a mine field.
- Mine fields must be defended by artillery or other rapid response forces. Give the enemy the opportunity to clear your mines and you've lost your investment. Let the enemy have just 1 of your mines and next week he'll have a gizmo that renders them neutral. Plus mines are a force multiplier and should be used in a layered defense, not on their own.