I feel that if you add another faction that is similar to RU in terms of the number of factions, etc, that either it wouldn't stay healthy, and would be the weakest and people would lose interest in it. I think that the type of faction that could bring the largest success is a private military that has morals to support the losing side as you said. This would be just one faction, and that faction could have one group that would be the Special Forces of that private military. Simple as that, one or two factions (one would have the SF have the same uniform and weaponry, just be in another group of that original group). This is small so it doesn't pull too many people from either side, because adding a nation that is in similar capacity to RU/US would pull some good members from RU/US. If this 3rd nation had only one/two factions, it would truly be seen as the extra force that still has a decent amount of appeal. Let me know what you guys think. (This is very similar to what some others may have said, but it is explained a bit more in depth I hope.)