Stealth in space does not exist in the OTU, and can not exist in the universe.
perhaps you are going about it backwards.
consider modern submarines. active sonar works, but it gives away your own location. passive sonar is much more limited, and modern submarines are quiet enough that passive sonar emphasize listening, not for the opposing submarine itself, but for the noisy sea-life it displaces - for the "hole in the water".
your opponent may not be able to hide from your sensors. but won't your sensors give away your own position before informing you of his? by the time you get a sensor return, he will already have a laser shot on the way.
there is also the element of time. sure, given proper equipment, you can passively detect and locate anything - eventually. but can you detect and locate soon enough to matter? sure, you can detect and see and target incoming missiles - but can you do so with sufficient speed and accuracy to hit them?
detection is not the same as engagement.
again, I suggest compromise. anything in space is seen, but only items within "sensor range" may be engaged. adding a -4 to that "sensor range" to engage a small evasive body seems reasonable.