The fact that publishers haven't experimented with that implies they're not interested, which dooms any project like this from the start.
• Advertisers want subscribers because that's a proxy for wealth and often, locality.
• Only quite rich people are willing to pay for an ad-free newspaper. The Spectator is one example of such a thing in the UK (subscription only, no ads).
• A lot of subscriptions are driven by a desire for opinion and opinionated takes, often by a single star writer, not news and certainly not neutrally written news.
Extremely slanted opinion sells like hotcakes and subsidizes all the rest, but the market for drive-by micropayments for opinion is very small. This opinion-subscription-bias amongst readers is why Substack works and also the Guardian (the Guardian is 90% just opinion pretending to be unbiased news).