Earlier quoted context omitted.
Have you already seen the MNT Reform? https://mntre.com/reform/
Heh, I hadn't either. My dream machine has 4x NVMe, 128G of soldered on RAM (with power control), a real SDR, plenty of GPIO, ADC/DAC. 2x ethernet, serial, CAN, novena style fpga, second SOC cpu with dma... basically a hacked up LX2160A (for which the design files are available... but not open as far as I can tell). I tend to stick to a box for a long time... typing this on a t420s. I dont care about the battery, jus…
Your requirements probably aren't too far off of one of our Blackbird systems -- I suspect it's just the form factor (micro-ATX) that's the problem. You might even be able to do the pull plug for minutes trick with a suitably sized lithium battery tucked inside the slimline chassis. ;)