How about using red triangles for enemy, blue squares for neutral, and green circles for friendly as a basis, just to make the friend/foe part absolutely crystal clear.
Scan, designated and primary could be differntiated by using thin-walled red triangle, thick-walled red triangles and full red triangles for instance, or perhaps put a green box on top of the primary and have only one walled version.
Same with the neutral and Friendly contacts.
The challenge then would be to differentiate between datalinked contacts and your own. something non-intrusive, but unmistakable, like a blue box around the symbol, or a little green "D" at its bottom left?