The Hisokian Collective is an entity similar to what you are talking about. All member factions have autonomy to a certain degree, but also have specific rules. The rules are fairly common sense rules like "don't attack other members" and "don't abuse portal access". We allow our members to go to war with others freely, but do not support wars of aggression on a Collective-wide scale. That is, if you are the attacker you need to convince each individual faction to fight for you, there won't be a Collective Vote on it. However, if you are the defender and didn't bring the war upon yourself you can request me to set up a vote for war and if a majority says yes all members are expected to a) defend you, and b) declare war on the faction that attacked you. Even if the vote doesn't pass, you can ask for help from other members of le collective. Naturally, factions that are not PvP-oriented don't need to go to war, they can support the effort in other manners.
If you want to join send me a mail with the following information:
Faction Stats: This tells us about you as a faction.
Name: Naturally, we need to know your faction name.
Leader: Who is the leader of this faction?
Size: How many members, on average, does your faction have? Officers?
Capitol: What is your capitol city/location called, and what world is it in?
Type: (PvP, Roleplay, Resource, General Purpose, Dunno Yet, Construction)
Style: The general building style of your faction.
Goals and Reasons: This will tell us why you want to join the Collective.
Faction Goals: What does the faction overall wish to achieve in the future?
Leadership Goals: What does the leadership of your faction wish to achieve in the future?
Reason for Application: Why do you want to join the Hisokian Collective of Factions?
Why should we take you in? Basically tell us why we should accept you into the Collective. This won't be the only factor, but the more convincing a reason you can give the better your chances of being accepted.