1) Paratroopers can't kill units even if these units can't defend themselves and can't capture cities after a paradrop even if they're undefended or defended by non-combat units.
2) Paratroopers can kill units that can't defend themselves after a paradrop and can capture undefended cities or cities defended by units that can't defend themselves.
Well, this is an interesting inconsistency. Basically what happens is that each unit has a boolean flag for whether or not it has attacked already that turn. When paratroopers perform their landing, it eats up their attack for that turn so they can't then attack even non-combat units.
The game, however, does not consider capturing a city with no units in it to be an attack move and so a paratrooper is free to do that. This, I feel, is the inconsistent part. Capturing an undefended city to me is the same kind of action as attacking a non-combat unit.
Here are a couple other uncommon scenarios where this will pop up:
a) A knight attacks an enemy warrior on grassland. The knight wins and moves into the tile, revealing an undefended enemy worker adjacent to the knight's new position. The knight cannot capture the worker.
b) A knight moves to capture an enemy worker on grassland. After capturing, another enemy worker is revealed adjacent to the knight's new position. The knight cannot capture the second worker.
c) A knight attacks an enemy warrior on grassland. The knight wins and moves into the tiles, revealing an undefended enemy city adjacent to the knight's new position. As it stands, the knight can capture the enemy city.
My proposal would be to make it so that a combat unit entering an undefended enemy city is considered an attack move. This would be Roland's first proposal and also make it so that the knight in example (c) cannot take the city. I think this is the most consistent and logical approach.
Implementing Roland's second proposal and allowing paratroopers to attack non-combat units after landing would be more difficult. It would require some special case handling for paratroopers, and would also require the AI be taught to defend non-combat units in the interior of its territory.
Thoughts?