Personal Verification & Account Approval
This may require a bigger team of course to implement, but I just signed up for a freelance website and the sign up process, is actually an application to use this site. I was required to verify my identity via uploading a photo of my ID AND a verifying statement such as a paystub, utility bill, etc. And also address verification (or at least a mailing/billing address) which should be added to the account anyways since payment information is stored for subscriptions.
I know that twitch has a younger population so that may not work, but it may also be a better way to minimize hate content if people know that usernames WILL be linked to verified personable accounts. That information can then be stored only for account verification purposes so no one can create an account using the same ID twice. If an account is voluntarily deleted, they must wait 60 days to sign up again using the same ID. And banned account cannot create other accounts using the same address as banned account or ID.
Just an idea to deal with hate raids and being able to identify culprits. It may take down viewership or the creation of new accounts essentially, but I do believe this will make Twitch a safer place.
For existing accounts, give them x amount of days to comply with the new requirements prior to accounts being forcefully suspended or deleted.
A workaround will have to be established for minors or Twitch may have to have a parental feature or an age restriction verified by ID.