Oh, there would have been ways for improvement. It's only that Apple didn't want to. They decided for a setup that brought the design to its limits, but refused to adjust afterwards (such as e.g. bringing in new processors and less power-hungry graphic-cards, the latter also as upgrade for existing owners). They could even have taken the design and offer a "consumer hardware" flavor as the often-demanded xMac.
There is a third option: Expansion without cables (i.e. proprietary internal connectors) and via plug-and-play "Lego" boxes (see my
earlier post). All the necessary software is there and even hardware solutions do already exist (especially for the required high-speed, low-latency internal connectors).
That way everyone could configure his "personal Mac" from mini to Pro. And expansion over the lifetime of the machine is possible by additional boxes, sold by Apple. That way Apple could earn money from upgrades and present themselves as ecologically friendly by ensuring a longer operation of computer hardware, instead of the current glue, lock and throw-away machines in their portfolio.