I could do it, if you would like. I think this is how I would tackle it, but I'll see if anyone else has 2cents to throw in. Mines would be defensive only, no movement units. You could have various levels of mines. Early minefields would be primitive and easy to spot. Sea mines would start as basic barrels of oil strapped to a motion detonator, and as time progressed would become heavily fortified invisible highly damaging mines. while IED's would be cheap and weak, but easily spreadable mines. Late game minefields would be invisible until you ran into them and be more devastating.
Well, enough theorizing. I see a few potential problems, but I'm sure we can overcome them.
Mines would have to be a unit. Making it a feature like peatbog breaks forests and ruins improvements. There is no other way to do it.
How can a unit build another unit? If a Destroyer places a mine, it would have to be a mine-unit, but no current function exists for that.
Other than that, I don't see any real problems. Any suggestions from other modders?
so yea, very busy! 
