If you're not sure what I mean with federated, you can check out PeerTube. However, the same scheme would work with books, audio content, movies, games, etc.
Each media company could provide an API on their site to redeem content (login on their system, process payments/keys/coupons one way or another), and multiple clients could access all of these libraries, while offering their own added value on top of this.
Well, maybe not federated but distributed instead. The nice thing about federation is that it provides you with a portal for single-sign-on and discoverability is less of an issue without search engines.
I'm convinced that something like this could be built quite simply on top of existing technologies like ActivityPub or the Matrix protocol. However, "app stores" or media portals are sooo lucrative that everyone wants to keep the biggest possible pie to themselves without sharing development cost with others.
One way I could see such a solution appear is if the government(s?) were to subsidize its development and started hosting public-domain (old, government-funded) videos on it.