Interesting idea...
You can check with a "fired" eventhandler when the player puts one down, delete it and replace it with the satchel model from GB's editorupgrade. Classname is AAA807
Then add an action to the player to detonate (and remove it again when the player is out of range). When you click the action simply create an explosion at the fake satchel's position.
When the player comes close add a fake action to defuse it delete the fake satchel and add a satchel to the player's inventory. The player shouldn't know his dealing with fake satchels
PS : When you place a satchel object on the map you will be able to board it, because it's a vehicle. Simply locking the satchel should solve this problem. (maybe set his fuel to 0 too)
Ok, that's all theory, I'm sure a lot of other difficulties will show up when you try to write that script...
Passing the names from the created satchel objects in the action script are a problem...