They should link up with Viacom, Lionsgate, and maybe add in someone like A24? Viacom/CBS doesn't have enough either imo, Lionsgate, has a decent amount of popular franchises like Hunger Games, Twilight, John Wick, the "Fallen" franchise, Knives Out, etc, but they're still too small. A24 puts out more indie content, but most of it is quality.
None of those really have enough for their own service (CBS All Access is proof enough), but together, you could be looking at something successful. Although the question does become are you just starting Hulu all over again? Hulu was created as a joint venture by Disney, Comcast, Fox and Warner.