Is simple:
The Original plan for Volkssturm mobilization for third reich,was to recruit 6 million soldiers,but this number never was anchieved,so my suggestion to the volkssturm mobilization event is:
If the Player ,playing as Germany,reaches the maximun extendition of the mobilization,will fire an event with the name as "mobilization of volkssturm",this will give for the player 10 militia,2 dissent and -1 IC.
This same event will fire every moth,giving more 10 militia,2 dissent and -1 IC,this will fire 70 times,every month,to hit the 6 million soldiers
When the player desmobilize,will happen an event: "calling volkssturm back" that will remove all Volkssturm divisions,give it +70 ic efficiency and remove 10 IC
What do you think?