Having low end, mid range, high end becomes a development cost vs commercial sales thing. Nabu Casa is a business and ultimately they need to make money off hardware as the software is free. There may be a niche market for a high end system, with all the bells and whistles, but would it be commercially viable? Likely not when it is competing with the likes of Smartthings, Homey etc.
Most home users would be more than happy with a green, and maybe a Thread or Zigbee dongle to add the extra radio. A significant amount of users would not want more than the current Yellow offers with a CM4 installed. Most wouldn’t even need the power of a CM5. As far as up time, well all electronics can fail, but eMMC or NVMe storage are probably not really on the high failure list for majority of installs that are not really doing a lot of writing to the database, and not being used for media or CCTV or stuff like that.
A lot of the more advanced features in Home Assistant, and the advanced use cases, are only used by a small number of users, and they are usually the ones most active on the forums, so you hear these niche use cases maybe a lot more than the actual real world use case would be.
I love the idea of a niche high end system too, but this might be more something for the people who would use these systems to build at home for themselves. That’s the joy of having the software opensource and compatible with many platforms. You can pretty well build anything you can dream of. It just is unlikely to be commercially viable for a company needing to make money to pay for the development of a niche system