When you leave the Guild it's exactly like the games. You can move around freely and not have your activities controlled by the guild, but you don't get the full 100% of the reward (|D) and no longer sleep inside the Guild. You can become an exploration team with their own base of operations (Like Sharpedo Bluff if I use the games as an example) though you'll still have to go inside the guild to take jobs and shizz. A graduated guild member can also freely take missions from any Guild because as I said earlier, graduation enables the team to move around freely.
I don't think I'm going to allow for graduated teams to create their own Guild because otherwise the forum is gonna become overrun with them over time.