please give us a way to change masteries in game as long as we havent left the fountain.
i know this is a lot to ask for, but i just entered a game where due to an in client bug, my masteries werent updated, even though i changed them in champ select.
entering a game with the wrong masteries can have a ridiculous impact on your personal performance, and almost as often as the player is at fault for forgetting to switch, it happens on riots end that people end up with the wrong masteries on the wrong champion.
from a technical side this probably requires a good bit of efford to implement, but from a gamplay perspective it shouldnt cause any issues when players are allowed to switch masteries as long as they havent left the fountain.