You make the character and either the others in the roleplay play the other two or you use them are NPC's to use every once in awhile. My team consists of one main character two bending partners and the manager who will appear even less than the other two but is still needed for obvious reasons of managing the Silver Shark Whales.

 I'm not sure how battles in pro-bending would work because I have a team myself and more than likely they might end up facing each other which is something I normally avoid and for the fact that my team consists of very talented and very specialized benders who have won multiple championships due to their skill. So the best way to avoid a fight between them would be to put them into two different leagues or circuits.

The reason i'd prefer not to have a pro-bending team of players is because then it'd consist of them posting while the others either don't post or get in the way. And if it's just you then you need to micromanage multiple characters AND make their fights alongside the enemies.