I think that will just overcomplicate things. Right now, all Strings in Pharo are unicode strings.

Cool. I didn't realise that.  But to be pedantic, which unicode encoding? 
Should I presume from Sven's "UTF-8 encoding step" comment below 
and the WideString class comment  "This class represents the array of 32 bit wide characters"
that the WideString encoding is UTF-32?  So should its comment be updated to advise that?

Not really, Pharo Strings are a collection of Characters, each of which is a Unicode code point (yes a 32 bit one).

An encoding projects this rather abstract notion onto a sequence of bytes,

UTF-32 (ZnUTF32Encoder, https://en.wikipedia.org/wiki/UTF-32) is for example endian dependent.

Read the first part of

https://ci.inria.fr/pharo-contribution/job/EnterprisePharoBook/lastSuccessfulBuild/artifact/book-result/Zinc-Encoding-Meta/Zinc-Encoding-Meta.html

I love that book :)

This is too cool to have cool doc