The questions here are:
1) Is this a non-issue?
2) Should I try to design the game in a way that this is harder?
3) Should I just omit multiplayer?
The issue is that this will happen. Most people, if playing with a friend, are going to just up and form an alliance and then focus on each individual computer player until it's just human players left. This, of course, is inherit in the actual gameplay, but I feel that it will ruin the game.
1) I guess if the players have fun, it doesn't really matter and I shouldn't even worry about it.
2) I could make it either single player or all human versus human. There is already a defense against it in that if you start a war with one player, all of that player's allies are going to come to their aid. Any other ideas (if you think trying to design against it is a good idea)?
3) The best way to avoid the situation would be to just omit multiplayer. Not the best solution, but would fix the issue and would also shorten development time.
Any comments and/or suggestions would be greatly appreciated. Thanks!