Expandable motherboards - what devices do you know?

Question

Iron

I really like the concept of RAM modules external to the device, a video card, HDD, a bunch of ports, and even a powerful processor in my dreams, and in the main body to leave only the most necessary for functioning (SSD with the system, a minimum of ports (USB-C, USB 3.0, microSDX, jack), 4-8gb RAM, a couple of energy-efficient cores at 2GHz + a video card built into the processor). You carry the device itself (say, a tablet) with you wherever you need it, you come to work / home - opp, and you already have a full-fledged workstation. And all this is one device, one system, no need to set up any synchronization, etc. The only dilemma for the user is what to put on the SSD and take with you, and what to leave on the HDD, but SSDs are quite voluminous, so the question is not tough.
How is this different from a docking station? The docking station often simply increases the number of available ports due to some proprietary connector, it does not contain any valuable hardware that increases the resource of the device.
How is this different from one of the thousands of tablets with a keyboard? The fact that in those tablets in an additional module, in addition to the keyboard, there is nothing.
Virtual RAM via USB is obviously not suitable, you can also keep the swap on the SSD.
External GPU is not suitable, I'm talking more about proprietary things, rather than using existing ports for this (due to their poor efficiency).
Actually, I ask you to provide examples of interesting devices that implement this concept.. Comments on the feasibility of this principle and pitfalls in design \ use are welcome.
I personally can only translate Surface Book 1/2 from examples. The additional module contains a keyboard with a trackpad, an additional battery, a discrete graphics card, additional. ports (including 2 proprietary ones, to which you can attach more hubs)
The sad thing is that an external video card can also be connected to a regular tablet if the ports allow (and they are often a problem), the power bank too, and the keyboard and trackpad are more of a limitation, because you you can’t choose them yourself, according to your tastes, and then it’s easy to replace if anything.

Answer 1

They tried to release this before - it never took off. Most people do not need this, and a minority does not pay back the costs of the manufacturer.