If you are going to go lightweight, you might as well go full retard and get nanolinux or tinycore, both of which are Linux distros that feature GUI interfaces and clock in at about 16mb install size.
Command line only versions of Linux go all the way down to 2.8mb in size.
I've run them both.
Wait, wait....
A linux N00b will be totally lost, and I mean totally fucking lost with those distro's
(You forgot DSL too - in the same size range)
Yah, if you have an apple Lisa, or a commador II, you fuckin' A ! Run those distro's for the plain and simple fact that the CAS latency on the RAM in those systems is 2 - 3 !
Yeah, no shit - - Fastest RAM that was ever made.
The problem with those linux distros, is that you'll need programming skills also - which newbies generally don't have.
Everyone nowadays wants "Plug-N-Play". That's why I recommend VUU-Do.
The Distro's you mentioned are KICK-ASS if you have an ancient system (or even a new one and you know what the hell you're doing), and you can write BASIC, and know BASH. On a relatively new system - there is so much integration you have to write, you might as well sell the completed code as a new operating system.
No, you are exactly right - those are extremely light-weight OS's. But, you forgot the caveat that you need to know how to program - in fact , not just program high level and OOP, but at the assembler level (which runs sooooooo much faster - you're only one step away from binary).

Structured and functional programming are a totally different ball game.

Hey, thanks for the post, most peeps don't realize there are hobby operating systems out there that are designed for the average person to play with. Funky and fun.

EDIOT:
https://raymii.org/s/articles/Small_Linux_Distros.html