Re: 10KB for the OS?
kernel != OS
Besides, with flash prices being what they are, you can pretty cheaply get 1Gb flash these days, ram is more expensive, but even then, 8 or 16Mb would be more than enough for IoT, and that comes quite cheap.
A tailored Linux kernel would be much better, has much better support, been developed and gone through testing for 20+ years, and, best of all, drivers for chipsets are readily available. Not sure what the RAM requirements for systemd are, <joke>I guess at the least 2Gb</joke> ... but then again, who needs systemd when you do not need gnome.