Individual players don't give a game longevity. Since they play on their own, they don't have any sense of place in a larger in-game community - aside from the forums, which are always dominated by the loudest, most aggressive people in the playerbase. This means that they don't have a psychological investment, which is far, far more important than the small monetary investment represented by their one MC bought mech.
(This is the planned business model - selling time and allowing paying players to shortcut the grind. If you think 20-30 matches for a mech isn't a daunting grind, well, I don't really know what to say to you.)
What does give a game longevity is the friends a player makes in the game, and the sense of group membership that he or she develops with those friends. Instead of going out of your way to make it hard for large groups to fight any other format - and in the doing, preventing any group of size 5, 6, or 7 from forming - you should be focusing on making it easier for individual players to form groups. I don't know precisely how to go about this. Maybe players should be grouped before they even launch into a match. Maybe they should be able to send friend requests after a match. Maybe there should be a chat system for post- or pre- match discussion. They probably need a game-install level integrated voice chat that's set up for them by default. They definitely need a much more robust community system in place, and that should come sooner rather than later.
MWO, like most online games, will live or die on its metagame, not its regular game. The more obstacles and frustration you place in front of groups that strongly contribute to that metagame, the worse off you will be.
Make it easy to get invested.
Edited by wiegxodus, 12 October 2012 - 06:48 PM.