I think he is playing us!
The hardware requirements, as far as I can see, are all pretty much doable with off-the-shelf stuff. Of course, if you were willing to sport the cost of designing your own boards, you could do some pretty slick stuff - you could stuff a FreeDOS-type OS into ROM and make it a boot time option if you liked. You'd probably want to write your own single-tasking OS, so as to avoid the limitations of DOS, but it could be done. Personally, I wouldn't have much use for it, and if you chose to rewrite DOS properly, there wouldn't be much software for it except what you produced yourself, but you could definitely do it.
The real problem is on the software side. You could probably modify *BSD or Linux to get pretty close to covering the list, but it would take some major overhauling to strip it down without simultaneously rendering it useless, and certainly nothing comes out of the box this way.