Being a team leader could be like being a trainer of trainers. You battle trainers, use speeches to convince them to join your cause (like those games were you befriend enemies), you could be acompanied of maximum 6 of them wherever you go, the rest waits for you in the HQ (like pokemon in a PC box), and instead of becoming a champion you could have several (quite difficult) goals like conquering the region, destroy and rebuild your region, etc