I don't really think it fits with the scale of the game. 1 tile is meant to represent a huge area, many kilometres across, and I don't really think a minefield fits with such a large area.
Mines have been in other games in the past, and they're always incredibly annoying and open to abuse. For a while they were in loads of RTS games, and they always provide way more annoyance and frustration than fun. I doubt the AI would be able to use them effectively...... or at least, wouldn't be able to abuse them in the same way humans would.