That is why you make the progression dependent on either a single player or a majority of players, e.g. if 3 of 4 are in the map exit zone, you exit anyway or call a vote to exit where >=50% progresses.
We had that down as a possible feature, but decided it was still too detrimental to gameplay. Nobody wants to have to have a vote to move onto the next area. Nobody wants to be outvoted, or be in the middle of purchasing items at a shop when the other 3 out of 4 guys decides they want to leave. It is not a viable solution for the problem.
The point of an FPS/RPG is to take time to explore your surroundings and experience things on a slower pace than in a standard FPS. I guarantee you, if you decided to play through an entire FPS/RPG, you would end up getting pissed off on at least several occasions at such a system. Not only that, it doesn't address the issue of saving games, item distribution, quest distribution, etc. What happens when you get a story quest from an NPC, but someone else is buying items from a shop elsewhere in the map, or talking to another NPC? Should it just interrupt them and warp them to the quest NPC? Or should the NPC give the same quest out multiple times? Neither is desireable. It works in an MMORPG, but not in a story-based game like this. These are all issues that had to be dealt with and in the end, they just made coop inpractical.This comment was edited on Aug 9, 16:29.