I think this is a bad idea and easy to manipulate, as there's nothing that prevents the streamer or his opponents (even so called stream snipers) from betting.
Let's say I'm a streamer, or my friend is. We gather a group of people enter a game together and bet on him getting first blood and win. Then the person, who gets placed in the enemy team feeds whole game to make sure his team loses. This is just one of the possibilities.
Not if it is ranked games since you cant play with your friends, the possibility of getting a friend in the enemy team is extremely low
