HN is bad news for a "Land Mine" unit b/c everyone will hunt them down w/ a vengance...
however, what if you gave it ZOC, a mediocre D #, 1 A, immobile, invisible, a huge bombardment # (well, not too big but you get the idea), limited ROF (1 or 2) and 0 range on the bombardment?????
in practice, these little buggers could be pre-placed, air-dropped or transported to their destination and upon encroachment of an enmy upon its tile, it would fire off the big ZOC bombard and then engage in the battle which it'll most likely lose b/c of it's lower D #'s in comparison to the attacking (enemy) unit. thus, it'd be expended after it inflicts some damage. can it work though?