I have been watching this one for a while.
I have my current VOS build running in a VirtualBox with this OS and it is pretty fantastic for reliability. It definitely runs better than the other VirtualBox with FreeDOS.
There are a lot of ARM boards that seem to run really well with this, another reason it is a strong candidate.
Another big reason is that it has a modern HTML browser that can be run to link to localhost. FreeDOS only supports a simple text interface monitor for the server when it is running, you have to actually run a browser on another machine to connect in. I do this on VirtualBox no problem but deployed on a real machine it could be seen as a huge inconvenience.
UPDATE : I forgot to mention, it is also stocked with quite a few critical document viewers for things like .PDF and .RTF, critical to the memex library of searchable documents in Vault-OS. Another thing you probably won't see in FreeDOS any time soon. One installation would be a complete web server and workstation together.
P.S. The real challenge would be to get this running on a cheap thin client like an Evo T30, a computer you can usually pick up for one dollar on EBay plus S&H to send it. Since the Evo T30 runs FreeDOS you should be able to get this working on it as well. These thin clients often have specifications and MTBF that far exceed custom grade military spec computer boards. They are built to be tough and "just work" forever.