This solution to "network transparency" is nothing else than pushing the whole screen updates directly over the wire. So why not use established protocols like VNC?
For instance, sub-buffer updates have certain constraints that make it very fast in the local case but would require a lot of data serialized over a the wire every frame, and networks do not have the bandwidth for that.
"network transparency" is an anti-goal in protocol design for the same reason "rpc that acts like a function call" is inherently flawed - the network adds a lot of complexity and different design constraints.
Games that try to sqeeze every ounce out of the hardware with tricks for extra FPS are not suitable to be serialized. I agree with that.
So, the very abstraction of "textures, models, display lists, and draw commands" is no longer what is being managed by the graphics stack. That is just one legacy abstraction which could be emulated by an application or gateway service. As people have stated elsewhere, one can continue to operate something like X Windows to keep that legacy protocol. Or, one can run a web browser to offer HTML+js+WebGL as another legacy and low-trust interface.
But, one cannot expect all application developers to limit themselves to these primitive, legacy APIs. They want and need the direct bypass that lets them put the modern GPU to good use. They are going to invest in different application frameworks and programming models that help them in this work. I hope that the core OS abstractions for sharing this hardware can be made robust enough to host a mixture of such frameworks as well as enabling multi-user sharing and virtualization of GPU hardware in server environments.
To provide transparently remote applications in this coming world, I think you have to accept that the whole application will have to run somewhere colocating the host and GPU device resources, if the original developer has focused on that local rendering model. Transparency needs to be added at the input/output layer where you can put the application's virtual window or virtual full-screen video output through a pipe to a different screen that the application doesn't really know or care about.
If you purposely design graphics devices you can make many simplifications and optimizations because you can abstract all tasks as drawing primitives. That will make serialization very easy.
The core of the GPU is really computational data transforms on arrays of data. But there is a whole spectrum to these computational methods rather than just a few discrete modes. This is where application-specific code is now supplied to define the small bits of work as well as to redefine the entire pipeline, e.g. of a multi-pass renderer. The differences between "transforms and lighting", "texturing and shading", "z-buffering and blending", or even "ray-casting and ray-tracing" are really more in the intent of the application programmer than in actual hardware. The core hardware features are really to support different data types/precisions, SIMD vs MIMD parallelism, fused operations for common computational idioms, and some and memory systems to balance the hardware for certain presumed workloads.
> So why not use established protocols like VNC?
Yes indeed!
Serialized GLX was introduced by SGI before direct rendering was even possible. It is what the creators of OpenGL originally envisioned (Graphics terminals connected to servers). If anything DRI that came afterwards was the hack.
Serialized GLX doesn't make sense in every context, I agree with that. But it is great to have the option. X11 offers that option, Wayland does not. Of course you could write your own proprietary client server architecture on top of the Wayland protocol. But why reinvent the wheel?
Not whole screen. Whole windows.
You can use VNC, but it won't integrate well with other windows.