1. how to start a mission with a squad already loaded in a helo.
2. how to make helos land.
3. how to make helos shut off engines and wait.
4. how to make helos wait for squads to board.
5. if at all possible, how to make them hold position and deploy drop ropes, or rope ladders.
6. how to make passengers climb down ropes, rope ladders, or eject.
7. how to setup so that helos will deploy when called in by squad leader.
It looks like all his questions, excluding number 1, can be done with the BAS Blackhawks. You just need to have the helo as part of your group, or set up an event (trigger, etc) that will add one to your group when needed.
The following are solutions to your question, based on the fact of using the BAS blackhawks (or MH-47):
1. (Has already been answered)
2. In your action menu you will see "ORDER: Land MH-60L" or similar
3. When you order the helo to land, if it waits for a few seconds, it will shut down its engine. You can also manually order it to do so by using radio commands (F#>Action>Engine Off)
4. The helo will not take off or move unless you order it to, so it will wait for you and/or your team to board.
5. Again, this is done through the action menu, instructions are in the readme file that comes with the addon. It's very easy to use.
6. As with #5, read the readme for the addon.
7. If you have one already assigned to your group, and have told it to land and wait, then it will sit there until you give it orders. Another option is to add it to your group using an event, such as radio command, trigger, etc. The DAP version works in this way as well.
There are ways to do all of the above without the BAS blackhawks, excluding the fastrope and ladder stuff. But it requires a lot of scripting, so you probably would be better just using the BAS addons. If you would like, PM me and I'll walk you through all the details about those addons and how to use them in a fast and easy way.