I was playing the BTM_BASIC4.1 mod the other day, and I found a good use for a combo of helicopters and marines - take out the AI's damned radar towers!
This worked well until they had MI and MA defending the towers.
Basically, I had 3-4 helicopters full of marines (in BTM they have an attack of 10, while paratroppers have an attack of 8), and I would airdrop them around the city I wanted to conquer, near the radar towers. On the next turn, I would use them to attack the lone defender of the radar towers, thus removing the defense bonus of the defenders in the city.
This worked well until they had MI and MA defending the towers.
Basically, I had 3-4 helicopters full of marines (in BTM they have an attack of 10, while paratroppers have an attack of 8), and I would airdrop them around the city I wanted to conquer, near the radar towers. On the next turn, I would use them to attack the lone defender of the radar towers, thus removing the defense bonus of the defenders in the city.