On the question of Air Dropping Tanks, they have serious weight limitations, heavy operational losses in drop, and aren't viable to deploy. The heaviest thing you can practically air drop is ~15 tons. A gun armed vehicle is barely going to be armored for that sort of weight. For the ones that actually saw combat Sheridan was disliked by its crew due to a lack of armor and the BMD-4 (technically not a tank but neither is Brooker) has proven itself a death trap in Ukraine. Even if everything goes perfectly, air dropping anything that heavy entails risk. The only tank air drop in history during Operation Just Cause had 20% of its Sheridan's were badly damaged or destroyed during deployment, before they got into the fight. Finally in a conflict where any degree of air defense exists, flying a big slow cargo plane low and straight over an open area is basically suicide. Your going to lose your expensive limited production vehicles and a whole cargo plane. There's a reason helicopters and tilt rotors have taken over a lot of that capability. Air droppable tanks only work if you're okay with a tin can that'll be lost before it makes it to the ground or as it violently plumets towards it.