Using undocumented endpoints is at your own risk, so if things like the delete endpoint don’t work then you’re out of luck, you used these endpoints well aware they are not designed for you to use them so if one doesn’t work then it likely wont be made to work for you.
Should you wish to see proper support for this feature, the correct place to suggest it would be https://twitch.uservoice.com/forums/310213-developers and state what your justification is to need the features.