Daro,
There are several options: Artillery, Mortars, Airstrike, Apaches and Tanks. I couldn't get the last two to work. Somehow the Apaches crashed the game as soon as the embedded script for the explosion was activated.
https://www.youtube.com/watch?v=V3QphbWJviI
I never got around to figure out what was wrong and if I could fix it by tinkering around.
Using the tank was something else that I could not get to work. I am sure I could if I put more time into it, but again...never got around to it.
https://www.youtube.com/watch?v=c0cHchdbfxU
The options (for the Teamleader at the start of the game) are all set within the XML files. Teamleader dies? Another one will take over and have the same options, exept for the Airstrike and Artillery (if they are already used). Like I said earlier, the Mortar strike will reset as you can see in my video (XCOM) too.
If you would want to have these option to reset all the time, I guess you could do that too. Simply drop a timer beside it in the XML and have it reset after x amount of minutes when previously used.
You can see in the last vid that I (almost ) also had the MK19 working. Probably needed some tweaking too. Again...no time and I wondered if it was worth the effort (considering the amount of people playing the game)