Backstory: I've done a lot of business in the ecommerce space lately and I've tried to listen to any podcast in that field. I found it's not easy to pick out specific ecommerce related podcast episodes from shows like a16z, The School of Greatness and others.
The Idea: A curated list of podcasts by niche.
Deep Dive: You would have pick a specific niche and curate the first one yourself. You could eventually get user submissions to curate additional ones.
Take ecommerce for example, once you become the authoritative source for ecommerce podcasts you could either start your own podcasts and pull similar guests to appear on your podcast or monetize that niche through ads.
Validation: I've already created a small list of my own.
Monetization: This would lead into your starting your own niche podcast around a topic you're passionate about or becomes popular with your customers. Another route is to have ads on your pages to drive a small amount of revenue.