A reward for reaching a higher division is a full refresh to tokens, allowing players to play even longer instead of waiting several hours to play again. But once you reach division 1, I assume you can no longer earn those refreshes. This limits players who play the game religiously to even less gameplay

A mechanic in many similar games when you reach max rank is to reset back to zero. But since divisions also regulate the experience each player has, this would cause absolute gods of the game to fight absolute noobs

So, I suggest, new game +. You are still placed with other division 1 players, but personally, you yourself are reset back to division 10+, allowing you to continuously gain rank points, allowing even more refreshes, leading to more gameplay without effecting the servers