we got stealth ships, so why not a "stealth Bomb" or "stealth mine" although on an open board i don't know how you would track where it was placed? just more random stuff i think about...lol

Maybe a something like "at the end of the activation phase you may discard this card to drop this mine" and have the mine drop at a distance of a 1 straight - when it goes off it gives a stress token to each other ship at range 1 of the mine. That way no one can know if it was dropped before it is too late - and I think for something like that it would be too powerful if it did damage.