manipulating (capitalize, lower case) unicode bold and italic characters

[Dan Hitt]

In emacs, you can use CTRL-x 8 CR and then at the prompt auto-complete a
name like "MATHEMATICAL BOLD SMALL w" (without the quotes) and get a
unicode bold w inserted into your buffer.  You could also auto-complete in
a name like "MATHEMATICAL ITALIC CAPTIAL W", for example (also without
quotes).

This is extremely useful, because, for example, you can enter a bold face
or italicized comment in a piece of code, and the font will survive exactly
the way you want notwithstanding any font-lock or other rules that may
dictate some other style that you specifically wish to override.

So it's a sort of unqualified good, but it would be very useful to be able
to select a region of text, and convert it to mathematical bold, or
mathematical italic, or fraktur, or other unicode symbols.   (Right now, i
do copy paste for this, and would like something easier.)  It would also be
good to be able to change case easily (and i guess this should work whether
the characters are greek or latin, and work with arabic digits as well).
(And such a means should try to be complete enough to work on the other
unicode goodies, such as mathematical bold script capital R.  If a
transition were impossible, then the character in question should just not
be modified.)

Is there any code out there that does this?

I'm using emacs 24.5.1 on debian 9.

TIA for any info!

dan