> - to learn a particular input method by example, just by seeing how
 >   to touch type a character and typing it below~ without having to
 >   resort to searching that character in the Internet. I have needed
 >   such a feature many times.

What's wrong with M-x find-library RET chinese-cns-tsangchi RET M-x
occur <use mouse to copy character> RET, aside from being clumsy
(which you should expect from a proof of concept)?

With a little bit of effort (eg, limit the size of the popup window to
4-5 lines, sort shortest first so you get the single character, add an
option to pick the whole string in the region if the region is active,
add a mode which waits five seconds on each character in the example,
then prompts with the appropriate keystrokes, etc), that can easily be
turned into a generic tutor for any Quail input method.  But it won't
work at all for anything based on XIM or SCIM.

Another way to put my position is that by the time you've accumulated
enough diverse purposes for this feature, you have accumulated a bunch
of purposes that can be better served by much simpler special-purpose
programs.