I don't mean exclusively things that have NEVER been done. Things that have rarely been done are fine too I guess.
So I'll do an example.
I suspect this one is something that didn't get done often, if one can say it's happened ever, largely due to the "last son of Krypton" story angle that editorial apparently likes more than readers. In Superman stories there's been quite a few teen sidekicks. Full Kryptonian(Kara Zor-El, Lor-Zod), part Kryptonian(Kon-El, Cir-El), or other metas(Mon-el, Natasha Irons), there's a variety of them.
You're probably thinking 'but what's it missing'? Teen antagonists! Sure you don't technically NEED them, but stories with teen antagonists are just... different than adult antagonists. They've dabbled with this in LoSH because LoSH is mostly late teens early 20s characters. But rarely touch on it in the main books. It's the sort of thing they might have done with New Krypton... if they hadn't blown it up.
At any rate thought teen troublemakers feel like a natural counterpart to teen sidekicks.