The way I see decentralized file hosting (podcasting being a subset) would be through some sort of white listed permission based system. You explicitly need permission from the host providers and the interface let's you choose among them which to publish to (almost like paid relays but with extra restrictions). No idea on implementation 💁‍♂️ but I can't see any other way without it going really wrong ☠️

Doubtful on a formalized-trust based system which likely will be abused