I can suggest 2 options for the WT20- depends upon the workload that you guys have:
Option1: Entire World Cup-1 tournament
Have all matches into one game- right from qualifiers to the finals
Option2: Qualifiers+ Main
Divide it into 2 parts - One for the Qualifier and the 2nd for the main event.
If you go all in, it will be difficult with the limited number of substitutions on hand.
Option3: Qualifiers+ Group A+ Group B + Finals
Earlier we had this system in place for some of the older World Cups in 2011 etc. Works, but again, depends upon the FC team and its workload.