Hey,
As you probably know, after you accept a match, there are ~20 seconds of waiting for everyone to accept. Also, in league games, you also need to wait for your turn to pick sometimes. Usually in this time, I (and I believe others too) minimize the game for a bit while waiting, but the problem is that sometimes you forget to come back and choose your god, resulting in a Deserter pentalty.
My suggestion: You can make a notification (like the Match start and Match ready ones) that will alert you when it's time to pick a god, so you can avoid cases where you forget to pick due to long waits. This is probably not too complicated and can be really comfortable.
Hope this will help!
Have a great day.
~Sonic