I'm attaching a zip file with a demo mission including all the scripts and trigger code.
Its on Everon. When you preview it in the editor, be sure to hold SHIFT when you click Preview, as that will take you to the Briefing screen.
In the Gear section, the last man will be shown as "Gear Bag". Load him up with anything you want.
Once the mission starts, he will disappear, and you'll have all the "kmkSquadStuff2" actions in your action menu. One of those is "Drop Pack".
When you select it, an ammo box will appear 2 meters in front of you. It will all the gear loaded by the script "LoadGearBag.sqs", as well as whatever you selected for the "Gear Bag" unit in the briefing.
For documentation on the kmkSquadStuff2 scripts, see the "Pending Items" entry in the Editors Depot.
Hope this helps you! Feel free to post any questions about it.