Very good idea Rise! That wouldn't really change the mechanics of the game as much. PvP'ers wouldn't worry about increased burning of SDP, and stopping more than the occasional scout (short of adding 10m SSD or insane BFA) would be possible.
IRL, you're not suppose to know if you've been scouted. So how could you defend it unless it was a fail scout attempt? You can't. That's why spy defense pots aren't used on enemy scout attempts.
Long ago sdp were used during spying and frankly it really sucked *** to have 1,000's of pots burned. Hence the devs put a stop to it. Like Ashley said, develop your idea then present it. A "because I want it" thread will not work.