Not all parties meet in a tavern/library/laundromat/prison. Not every posse is a group of mismatched cut-ups thrown together by fate (destiny, not the RPG.) Some people share a bond from the start (the Fantastic Four, Challengers of the Unknown) or just train like there's no tomorrow until they act as one (X-Men, ... Power Rangers?) Sometimes teams like these are even allowed in roleplaying games.
Teams already have benefits. They're great for team combat for one thing and a couple of guys with the right cliche to guard your back and provide a cliche you need is enough to turn a bad day around. A team could also be part of a larger organization and have a hook. For example join the Green Lantern Corp; get the most powerful weapon/tool in existence and see the Galaxy but you have to follow the orders of some little blue guys with big heads. Join the Holy Order of Justice and become a paladin but no more diddling the princesses you rescue. Or the X-Men can be viewed as a small team part of a larger group (human mutants) they want to help protect.
Aside from material benefits (power rings!) teams can have interesting benefits (see my earlier postings on equipment and sidekicks.) Some teams have a reputation, famous or infamous that precedes them. Even if the locals don't know you from Adam they will spot that skull logo on your spacesuit and know what it means. Being on a team may open some doors for you and close others. Police are more likely to share information with other police for example. Criminals might take one look and make you for a narc.
Let's look at some twists a team will allow:
Asymmetrical teams- A lot of superhero teams are like this. In the Justice League you go from Superman who can shift small moons to the Green Arrow, inventor of the boxing glove arrow. Note that I love all the so-called minor leaguers. When you're talking about power levels though the gap between Superman and someone like Green Arrow and the Elongated Man is pretty hard to account for just by choice of cliche. You can make the case that the Man of Steel has a few more dice than his cohorts (see my earlier post on epic characters.) If he got extra dice why didn't they? The simplest answer is he got them from his team mates when the team was set up. When creating characters everyone can contribute one or more of their dice to a player designing a big gun. The downside is you get less dice. The bright side is you get a superior character watching your back and can develop your character in other directions. As an added incentive the contributing players may each choose a hook for their big gun. The recipient does not have to take the die or the hook. If the demi-god does not do right by his contributors the GM is encouraged to go to the players for suggestions on how to deal with his bad teamwork. Sudden power loss works wonders for supers, mages and psionicists.
Questing Dice Pool- Instead of contributing dice to a character people on a team could contribute Questing Dice into a pool. This can represent team spirit or whatever. The players can decide they each use the dice in a different way or that everyone uses the dice in the same way. So the infamous League of Ambitious Antagonists sets up a dice pool and allows everyone to specify how they will use the dice individually. Razor Brick, the muscle decides he'll use the pool for 'Breaking things living and non-living.' White Collar decides he'll use the dice for con jobs and grifting and The Epic Brain will use the Questing Dice for designing infernal devices. The clones of the Conformity Crusade decide to create a Questing Dice pool and use all the dice for 'Fighting alongside your fellow clones.'
Merge- The Team can form an incredibly powerful individual. The being is created using the rules for Shield Mates but can have one die more in its highest cliche than the highest player cliche. The GM is the final word on how many dice you can put into the Merged Being. When the merged being is formed the rest of the group suffers some kind of drawback. Either they each lose the use of their highest cliche or are fused together with one member controlling the greater being.
Rallying Cry- Assembly Avenge Me! Or something like that. The team leader issues a rallying cry before the fight starts. The first round of a combat the team members may treat their appropriate cliches as double pump cliches. This is an excellent tactic for blitzing a boss or overpowering threat. Hit it with everything you have pumped up and hopefully knock it down to your level for the next round. The GM might want to reduce whatever cliche the team leader uses to order the gang around by one die for using the ability. The GM might also want to assess penalties to a team acting without its leader.
We Are All Individuals- Even teams or organizations that have standardized training and equipment will have members who use that equipment or training in their own way. The Jedi developed the Force powers they felt more comfortable with. The Green Lanterns used their power rings to create energy constructs but no two Lanterns used the same constructs which ranged from giant swords and axes to MRI chambers. This can be handled by rewording each member's cliche and giving different TN for different tasks.