Well the existing eGPU docks all have an individual design for the board, the case and the power supply. No chance to replace the power supply with a quieter or more powerful one. No chance to get a larger case for a larger graphics card. How about water cooling for the GPU?
Here is the whole case modding community to think about. People needs and tastes are different and a complete device will always be a compromise. A generic board that fits into the existing ecosystem would allow for a lot more specific setups.
Comparing the size:
Razer Core: (H) 131mm (W) 206mm (D) 321mm
Lian Li PC-Q01: (H) 275mm (W) 200mm (D) 242mm
The Razer Core is to large (depth) for my desk. The space on my table is only 25cm. It is still the best fit at the moment. The others are even larger (Asus Rog XG2, ...) and I really dislike the brutal design. The AKiTiO Node has no USB so I would need an additional TB3 hub and hope that it works with it, just to connect the input devices.