Just a minor point: the US Troop Carrier Command did operate assault gliders up to the late 1940s, including some joint exercises in the Canadian Arctic. The Canadian Army also used war surplus gliders in these same exercises. They were employed as back up to paratroops dropped earlier, bringing in things that couldn't be air dropped at the time like vehicles, artillery and long range radios. From everything I've read, the exercises all showed the gliders were not cost effective, being one way vehicles plus having a high loss on landing rate, even when coming into secured and surveyed landing sites.
What killed the glider was a combination of helicopters, and long range transport fixed wings that could open a big back door in flight.
One big draw back to the drop ship, at the current technology, has to be the obviously one way nature of the mission. Western countries today have a hard time getting volunteers for out of country missions that don't include cheese burgers (for the Americans) or Timmies (for the Canadians). I don't think you would get many volunteers for a quick ride to the centre of Russia or China if you told them they would have to walk back. Now, give them a stealth VTOL transport that will come back in a few hours, or even in day or two and that is very different. I think we will see that before we see drop ships or even suborbital one way missions, both from a technology viewpoint and a utility viewpoint.
OBB's scenario includes a massive WW3 type follow up to extract the intial small team and a few civilians. How likely is that type of mission into a nuclear power today? If the enemy is not a nuclear power, and not the size of a Russia or a China, V-22s and their stealthy followups will do just fine.
