I think they should exist. But not mobile, or offensive units. Being able to defend your base from Radar, or sneak in and hide a defense closer to your enemies base, would be Amazing. I also think that Advanced Fabricators should have some sort of technology to avoid Radar Detection. (But no offensive unit should have this ability) Just think about all the things you could achieve with this in-game. Sneak a few Advanced Fabricators in, build a radar Jammer, start building Artillery (turn off their power till you have a half-decent amount of defenses up) then turn everything on all at once.
