For example, the scenarios could include the following:
1) Race to Dunkirk (May 1940) - the player must prevent the evacuation of the BEF by (a) capturing Dunkirk and (b) allowing less than (x) amount of British transports from reaching the UK.
2) Operation Sealion (September 1940) - the player must land in the UK, capture London, and maintain control of certain sea hexes to permit naval supply of the army.
3) Operation Felix (January 1941) - the siege of Gibraltar. The player would also control certain units in the Spanish army.
4) Operation Typhoon (November 1941) - the player must occupy Moscow before both the Russian winter and Siberian units arrive in full force.
5) Operation Herkules (May 1942) - the invasion of Malta. The player would also control certain units in the Italian navy (naval warfare is a little underrepresented in Panzer Corps).
6) The Siege of Leningrad (September 1942) - the player must occupy Leningrad. The player would also control certain units in the Finnish army.
7) The Battle for the Urals (1944) - the player would have to push the Red Army behind the Urals.
These are just a few ideas (which I'm sure could be added upon once some North African/Middle East scenarios are developed). By having this DLC be a separate campaign, there wouldn't be any issues with integrating these "What-ifs" into the existing DLC's, and at the same time permit some (major) deviations from what happened in the history books.

