Include DBS checks with affiliate and partner onboarding
There is nothing currently in TOS that prevents anyone with a criminal record in casting - including people who have been convicted of race, hate or crimes. As a private company, Twitch could make the step to update TOS to prevent people who have been convicted of race, hate or crimes from casting - and make a DBS part of the onboarding process (a DBS is mandatory for teachers working with children, people in the care industry etc - why not on twitch when children can create an account from the age of 13?) . It wouldn't solve the problem, but it'd be a start - and make it easier for Twitch to remove those who pose a risk now and in the future both online and at IRL events.
Anything that makes Twitch safer is a good thing!