[Edi]

You don't need to have the #victorycondition command in the map file to use that. Just select it during game creation.

If the command was added to the map, then it would always be enforced in all games played with that map. I suggest tossing something like 30% to 50% of the VPs as the threshold, or even 20-25%, depending. It's a huge map and you'll run into micromanagement hell with standard conditions.