Hi Moon,
Ok, I mostly understand what you want to do. Do you wish to make the buggy drop zone flexible... according to the player's wishes...or will it be the same spot every time?
I have used David Berka's helidrop scripts for carrying and paradropping vehicles. (available in Editor's Depot) It works well, though there is no visible rope/cable attaching the vehicle. However, the drop part occurs when you place a variable ( release1 = 1 ) in a trigger (or WP) signalling the script to drop the vehicle and produce the parachutes.
So you might try using his script if you just want the vehicle to drop at the same area every time. Or why not use an
addaction command for the pilot and make it be the release variable for the script?
Notes: I used David B's heli4drop script for heavier vehicles ...gives you 4 chutes per vehicle. Also, you may want to adjust the height of chopper above vehicle, because it may cause crash for some vehicles.