you cannot be a gym leader in the games you can only fight them... ^_^
its easy think it
The fifth gym leader in Pokemon platinum is crasher wake but you get the fourth badge.
The water Pokemon gym leader is in Pastoria City.
The Gym Leader of the Snowpoint Gym.
The eighth gym leader in Pokemon platinum is the one in sunny shore city.
You use your strong(est) Pokemon to kill the Gym Leader's Pokemon.
Do you mean a gym leader?
The forth gym leader is in Veilstone City
by beating the gym leader
You go on to defeat the eight gym leader.
The 6th Gym Leader in Pokemon Platinum is Byron in Canalave City. He specializes in Steel-type Pokemon and has a Steel based Gym that looks like a construction site.
No, it is not possible.