The problem is that the submarine would have to come up on Link 16 to both receive a basic tactical picture (the problem is that the SUBMARINE wouldn't have sufficient siutational awareness without external cueing) AND report their overall tactical situation. People tend to get a wee bit suspicious when they detect datalink signals coming from an otherwise empty patch of ocean. Once again, this idea compromises the sub's stealth.
Most proposals I have seen for SUBSAMs involve a mast-mounted box launcher, loaded with Stinger. There was a SIAM (Self-Initiating Antiaircraft Missile) project in the late 1970s; this would have used acoustic sensors to detect overhead patrol aircraft or helicopters and could be left as a sort of "SAM Mine" to help a submarine escape.
ALL of the SUBSAM proposals have had one thing in common: the submarine community has said, in unison, "We are NOT toting those things on our boats." They have too many negatives (a submarine's only defense is stealth; these weapons tend to compromise same) and not enough positives to get Fleet "buy-in."