I did Linux from Scratch about ten years ago. I learned a ton. I actually did a few more installs here and there of it. It really helped me to understand the boot process and getting different devices to work.
I've never been in a position where a system only had serial as an option. I've used it to capture kernel output, but not really interactively.
As for BSD, I like the GNU flavor shell utilities, the BSD ones have weird flags. Maybe I'll try out the Debian flavored BSD...