kakashi is kage level for many reason one being his ability to access most situations and make a pretty good plan. he is very reliable as u also stated early on. he taught to two main characters n the story there elemental chakra ninjutsu (Chidori,Rasen-shiruken). also as stated they put him up first to b kage after tsunade went into acoma. his name is known world wide as the copy ninja he has over a thousand justu. He was a captain at a very young age also jonin. N he usage of kumi seems to increase the more he uses it theres much more but that right there put him at kage level to me and kage arent based off just physical and ninjustu skill any more u c all that paper shizune brings tsunade u need brains and the ability to protect.