Not really so close, though right? Using Laptopmedia's database, the only mobile ECC workstations are Xeon not Ryzen, and the minimum size for those are 15.6".

Not really so close, though right? Using Laptopmedia's database, the only mobile ECC workstations are Xeon not Ryzen, and the minimum size for those are 15.6". 16:10 is the best ratio you can get for displays. In fact, AFAIK, there are no current COTS laptops with a 4:3 aspect ratio display at all. I suspect if all of what you listed are actually hard requirements, the only way you'd ever get that is if you built your own - source an industrial 4:3 panel+controller, find the smallest Ryzen board with ECC support and get a Ryzen Pro APU (none of the ThinkPads will boot ECC SODIMMS on their boards, despite Pro APUs having nominal unvalidated ECC support) - you could try your luck with an A320TM or otherwise, might need to go embedded Epyc and an M.2 display adapter (like the SM750 ones). You could probably build a "tablet" form factor that's reasonably thin (<30mm?) and light (and use an external USB-C PD compatible chargers/battery packs and simple DC conversion to make life easier on the power side).