If I may, just my personal thoughts....
I've come to the conclusion, although obviously not ideal, that any modern 'Air Droppable' Light Tank will need to be designed with the reality that's it's survivability is going to be limited in terms of armoured protection. That it's operator - the US Army must come to the conclusion that it can not and will not have the armoured protection of an M1 Abrams, no matter how hard they try - period.
I think the Soviet/Russian Airborne sensibly knew and appreciated this as far back as the ASU-57.
Am I right to say that any Airborne Light Tank realistically has to rely on its compact size, shaping, speed, and armament to maximise it's survival rate? To employ it's firepower for as long as practically/tactically possible, until either their shock tactic of capturing a given target is completed or they are relived by heavier/more numerically larger conventional forces, which can meet enemy with like for like combat capability and firepower.....
Again, I think the Soviet's/Russian's appreciate d and came to this conclusion some 60-years ago.
Also, if I may, I think it's safe to say, that the lack of serious use of the M551 Sheridan by the US Army in any real/serious combat operations throughout its use within the US Army Airborne ORBAT, let alone any real emphasis to replace it, seems to emphasis to me that either the US Army is reluctant to use its Airborne forces in any serious matter or they instinctively know and appreciate the futility of such limited/vulnerable airborne armoured assault vehicles period.....
So personally, I've come to the conclusion that:
1/ The US Military/Political willingness to actually employ the likes of the 82nd Airborne Division in its intended role and capability as an airborne shock force in its entirety makes me question the money, time and effort for such a program.
2/ Any Airborne Light Tank has a limited survivability from its conception, due to the realistic need for its size, dimensions and weight limitations.
Although all means possible should be practically sorted to maximise the survival of such a Airborne Light Tank, the US Army should not, can not lose sight of the reality that a Airborne Light Tank can not and will not be a M1 MBT no matter how much time, effort and money they spend.
3/ US Army doctrine seriously has to determine tactically where and when the employment of Airborne forces will actually be employed and what the real calculated offs of their survival are.
4/ The principle purpose of an Airborne Light Tank is to facilitate the carrying and employment of heavy/high velocity weapons for both assault and defence. If there is a reluctance to employ such a vehicle/weapons platform because of its perceived 'survival' vs its intended role and purpose of employment as a weapons platform, then is it really needed at all?
5/ Going by actual combat history from Post-WWII of the actual intended use and employment of the 82nd Airborne Division in its parachute deployed role and intent, I guess the true question that needs to be asked - if the US Army/Political Administrations aren't prepared to use the 82nd Airborne as a shock unit in mass, by means of parachute, is it's existence and the cost of its existence really warranted?
Anyway, these are just my thoughts and I apologise if I've detracted from the principle topic/subject.
Regards
Pioneer