This is what the cloud is for. You're now going to tell me that you don't like that and would prefer local-only storage, but it seems like the vast majority of home and corporate users prefer otherwise.
> Use the same cpu/ram/gpu for both.
.. attached to your display and keyboard by a single USB-C connector. Or I suppose Miracast.
This turns into "would you like to buy a surprisingly not-cheap dock that's useless without the phone, or a separate computer that's properly adapted for its use case". Like 3D movies, it's something that the industry periodically comes up with, pushes for a while, and nobody actually wants because the compromises are too much of a downside.
It's far more likely that "smart home" and "smart TV" stuff will, very slowly, converge into a single integrated ecosystem where you can easily use your phone to control Netflix on the TV. "Casting" (a la chromecast) shows the way forwards.