Honestly if you want the games poplulairty to go further up..
Introduce a yearly player submitted champion design contest. Winners champion concept gets accepted and the winner can work side by side with the new separate group of designers from Riots new department of this would-be yearly event. Then the concept will come to life and be put into the game. Let the contest last a month. Like the last month before the season ends, then in the new season reveal the new champion.