Streaming from one platform to another is always going to be tricky, for a multitude of reasons. I don't see platform holders allowing this kind of functionality, instead of just buying the game itself on their own platform. They don't like that kind of competition.
It will be interesting in seeing who will GreenLight the PC Streaming App. It seems MS might allow the use of Streaming PC games to X1 since that seems to be RainWay's priority.
I can see the benefit in allowing PC exclusives to cross over to consoles, games from Blizzard as an example plus with Keyboard and Mouse support it brings more options to the systems.
The bad i see is what you mentioned about customers not buying from there own store, unless the console maker earns royalties from the App.
It does bring games that are not on consoles to consoles aslong as the customers have a Keyboard and Mouse at hand. In that case i dont see any issues with that. Its not for me as ill always play my PC games on my PCs.