Take the design of the new Mac Mini.... sell different versions for different CPU's as bases.
ie: Choose your base: Core i7, Core i9, Xeon W (8, 10, 14, or 18 Core), etc... and then how much RAM you want.
Then, in the same size case, sell a high powered eGPU..... and then let people daisy chain (stack) as many together as they want.... just drop another one on top and it all syncs together perfectly.
So the maxed out version would be like an 18 Core CPU base..... with 4 GPU's stacked on top..... kind of like a PC that has 4 GTX 1080's linked together with SLI.
Then you have a "modular" design..... and in the future, they could sell updated version of components to swap out on your stack.