He could go with Debian from Scratch....
If you ever get Debian booting in "a few seconds", let me know ;)
I don't think there's any operating system that will completely satisfy this list. I mean, the thing about booting into a single-tasking DOS-style OS, well, that rules out any Mac hardware - there's no native solution for such a thing, and you can't boot MS-DOS on Intel Macs. Which leaves you with Windows or Linux, basically, neither of which will satisfy the boot time requirement. Nor wil