Sure would be a wild card.
I'd also suggest that larger armies would be more vulnerable. Players could pay extra for minesweepers. But they'd never know if an enemy deployed mines around a held territory.
Also, there should be coastal marine mines. Navies would be vulnerable.
Mickey, I'm a Navy vet. I'm still waiting for force specialization so I can commission a fleet of Arleigh Burke class frigates, and a GOOD GRIEF!
I'm a geezer, a bloomin' geezer. They've actually decom'd the Ticonderoga?
I might as well lie down and die now. Maaaan . . . .