As Gevlon astutely points out in the comments on the last post, there is a basic flaw in Extended PvP (PvP carried out over multiple game sessions). Players will defect to the winning team. PvPers often talk about looking for good fights. But when you look at their behavior, they'd rather join the best side and steamroll the opposition, rather than do their best and lose narrowly. Sometimes it's even a self-fulfilling prophecy. Everyone believes X will win, and thus everyone joins X, leading X to win.
Transient PvP doesn't really have this problem. Since teams are formed anew at the start of each game or play session, matchmaking and randomness can generate teams with a reasonably equal chance to win. Or if a player finds themselves on a bad team, well, next game or session might be different.
So then the question becomes: How do we incentivize players to stay on losing teams, or even join the losing side? Can we also do this without incentivizing people to lose on purpose?
Perhaps we can do something with the reward structure. Maybe the faction with a losing record gets a higher number of guaranteed points win-or-lose, and an even greater number of points when they win. The problem with schemes like this is that you have to be very careful, or there will be an optimum point where below you want to win, and above you want to lose.
The only other idea I had was the winners automatically absorb the losers. Like if Faction A defeats some of Faction B in battle, those Faction B players become part of Faction A. Of course, this might lead to a positive feedback loop, where Faction A becomes quite large and ends up winning everything. So you'd have to build in some incentive for A to "split" apart.
Multiple faction games can make the equilibrium more stable. But there's still a possibility that one faction will end up overwhelming the others if enough people defect. As well, there's also the issue that the factions may opt for stability, rather than trying to defeat the others. Arguably, Eve Online has fallen into this state. The major players all have their own empires, and are fairly stable apart from minor skirmishes along the borders.
What other possibilities are there to keep teams or factions balanced in Extended PvP, while still keeping things from stagnating?