Hey Mike, I'm noticing a wee bit of a pattern to your posts - your not an M113 jockey by any chance are you?
Don't get me wrong, I fully agree with most of your points especially lightweight tracked armour to support para troops or amphibious landings etc.
The M24 would only have been useful as fire support for anti-personnel work, it was not a good anti-tank platform. The 75mm gun would not really have been much use against the Korean T34/85's, they out ranged and out gunned the lightweight Chaffee. Germans found that their 75mm L48 gun (Pz IV, Hetzer, Jag IV, STUG III and IV's) could struggle against the frontal armour of the 34/85 and that gun was
FAR superior to the Amercian low velocity 75's. They would certainly have been a great help though, and used properly in defence or ambush a very useful addition to the Task Force.
The limited Airborne armour that the Brits used in WWII was even more handicapped due to them having to have wafer thin armour and limited fire power. The tanks we dropped in by Hamilcar gliders (Tetrach and M22 Locust) were often easily outgunned by German Armoured cars and of very little use in an offensive capacity other than light recce.
An M22 Locust de-bussing from a Hamilcar: 
Modern forces have similar problems, any lightweight vehicle mounting a decent tank killing gun is normally too thin skinned to trade any serious punches with an MBT. Some of the lighter MBT's can be airlifted but are not really viable for airdrops as they tend to mean 1 plane per MBT = EXPENSIVE. We can see what tactiticians hope to achive by using the likes of the Stryker MGS, AMX10RC or Centaro - fire support but not really tank killers. Usefull for attempting to hold the ground until the heavy mob can trundle in and take over.
The French made AMX10RC, lightweight with a big gun and quick to get out of a fight - hmm a bit like their army and MBT's then? 
As with everything now the situation is fluid, perhaps the best way is to intergrate larger heavier IFV's wth limited anti-tank ablities (ATGM launchers etc) into the Airbourne mix. The Russians have done this for years with the ridiculous and cramped BMD family, but their more capable and usable BMP2 and 3's are light enough to drop from modern transport aircraft. As the C130 Hercules takes more of a back seat (to be used for more tacticle situations) and C17 Globemaster is used more and more, there is no reason why these planes could not drop Bradley or Warrior class vehicles into help the guys on the ground.
BMD1 - Tiny and toylike (same turret as BMP1 = 73mm smoothbore and AT3 launcher), you must have to be an Oompa Lumpa to crew one! 
In the long run we may achieve the holy grail of a well protected and armed airportable machine, it perhaps may be decended from one of the current 'Plastic' vehicles being developed or be even more exotic, sporting electrified plasma sheiling (being developed in the UK by DSTL). Time will tell, but as always costs and practicality will be the real deciding factor.
A Warrior hull suited up in electrified armour defeating a RPG round: 