I usually play on small map as that is the default, and I dont particually enjoy managing 20+cities. But in small maps, you have 5 enemy - and you have 5 alliance possiblity. 90% of the time I play for some peaceful victory, or roleplay a peaceful civ, and I always able to ally all of the civs very early. This fully removes the point of alliances with wars - if you are allied of both civs who goes to war, you will not be dragged into the war. It should work in a ways of real life - you would need to choose. An even if you are not go into war with any of them, the alliance should be cancelled with both, and grivances should be generated. What do you think?