I'm pretty sure I posted this somewhere before, but I don't think many people saw it. It is an old idea, and I think the original designers of Beyond Protocol thought of something like this (there is a very brief reference to something like this in the old game guide). The idea is that there would be an additional resistance available in the armor designer called Stealth or even just simply Radar. What it would do is give a unit protection against being seen through detection radar. If the unit is within visual range, it would not work and the unit would be seen and targeted (for protection from being seen in visual you would need a special like Cloaking). Once outside visual range, the armor would protect it again and instead of the green blob silhouette showing it would be entirely invisible. This also would mean that weapons that would normally continue to fire at a unit once a unit is out of visual range, but within detection, would stop firing. Maybe the Stealth property would also act to degrade the radar accuracy of units trying to target the protected unit, maybe would also make it harder for missiles to lock on it, though maybe these additions would be too much. Stealth would be available with starting tech, though maybe would have some specials associated with it that would offer bonuses of some kind. By itself it could be used by even new players to better hide their units, though later (if Cloaking was a tech: see Sniv's New Specials proposal) it could be used with Cloaking for greater effect.
To counter Stealth you would need something like two points of Detection (or maybe PD Accuracy) for every point that a unit has in Stealth. If you successfully counter it, the unit silhouette would appear when the unit is in detection range as normal, and perhaps any other Stealth effects would be negated.