So far I’ve found everything I looked for, and a few new ones too. Their app features for lyrics and other songs you might like work great. Admittedly, I’m an old metal head who loves singing to a song at the top of the voice, out of tune of course, so I might not be skirting the kinds of niches you like.
I think there is another aspect that is important: limit the blast radius. Shit inevitably happens when you create something new and complex, and when it does, you’d rather minimise the impact where possible.