95% sure the onebox already does that. If there’s enough information to display a onebox, it sure will, even if the content is ultimately paywalled.
What I think happens is that the onebox is getting denylisted by these paywalled websites due to recent LLMs crawlers/agents so it doesn’t see the same HTML we might see when using a browser.
Though, happy to get proven wrong. If someone wants to have a quick look to see if they can improve it somehow, pr-welcome 