Yes, I totally understand what you're getting at in regards to LOS control and elminating unnecesary POIs (points of failure, i.e satelites etc) HOWEVER as I stated before to have LOS control the J20 has to be relatively close to the fight and this presents an immense risk factor to the controller aircraft.
From a technical standpoint LOS decreases with operational ceiling and certainly during the ceiling of engagement. A competent enemy can easily 'trick' the fight on the drones and uses IRST or other methods to take out the J20 where detection range is not that much different than range of control for the drones. You are also assuming the fight is over neutral airspace where they is a clear definition of 'good side/bad side) and that is not always the case. The J20 and her drones could be well inside enemy territory during the engagement process. or be in an area where it's potentially expose to enemy air defense net.
.. and all this again is assuming the J20 or control aircraft has an RCS and other stealth characteristics that is totally100% reliable and presume undetectable from all angles by known opfor sensors and weapon systems. Like most 5th Gen ... we already know J20 is much less stealthy from behind than front.
IMHO the risk in controlling drones from another fast mover just behind by a few dozen miles or even a 100 miles is FAR too great and does not make tactical sense to me when similar capabilities can be achieved by a couple of very well rested, stress free guys sitting on a ground station deep inside a forest or inside an air conditioned tent in a green zone couple hundred miles away.
I can almost guarantee you that regardless of how 'safe' it is, no human pilot is going to have warm fuzzies focusing on remote piloting drones while he himself is strap into another strike aircraft flying just a few miles above/ behind.