1. Not sure if it is exactly what you are looking for, but about a quarter of th way down the page you'll see a carpet bomb script you may be able to modify.
http://www.tacticalgamer.com/armed-assault-mod-mission-development/144932-tactical-gamer-script-bank.htmlI know i've seen a better airstrike script elsewhere, so if I find it again i'll update this.
2. One of the respawn options built into arma 2 is to respawn at a certain point. In your description.ext add the lines:
respawn="BASE";
respawndelay=30; (30 seconds; change to want you want)
and you then place a marker on the map (empty for invisible) named respawn_west (if you're using USMC) respawn_east for Russian, and there's also civilian and independent.
Perhaps not the best but easiest solution would be to use a high respawn delay, so that late joiners won't spawn before the UH60 already makes it to its destination.
3. Group spawn for AI is built into the editor now. Once you place or create a group of AI units, double click the group leader to open up unit editor, give him a name (for this example i'll name him grp1) and lower the probability of existence slider to where you'd like (you can see the value when you hover over the unit after.)
Then open all of the units under him, and set the condition of presence to: alive grp1
This way the rest of the group will only spawn if he spawns.
Hope it helps.