What I think is this: if there are people who want to write it, and
people who want to read it, no matter the number on either side (as
long as it's more than 2 or 3 people total), it's rediculous to send
down an iron fence in front of them and say "Andrew Lih and Jiaqing
Bao do not believe you should be able to build a separate Wikipedia
for this language. Your request is denied."
Similar things to what you said can be said for many minority
languages, including for example Sicilian: Formal writing is usually
done in Italian, but that doesn't mean Sicilian doesn't exist. Basque
speakers often write in Spanish, and Luxembourgish speakers often
write in German or French, but that doesn't mean their languages don't
exist or that there will be no audience for these Wikipedias.
The problem of audience and readership is a problem for the individual
Wikipedias and not the Wikimedia organization, as long as there is the
"potential audience" of people who can understand the language when
spoken or written (again, there are technologies so illiterates can
take advantage of this technology).
You may see zh-min-nan as having "withered", but it's still growing.
It would probably help if it had some instructions for the
non-initiated on how to read peh-oe-ji, but nonetheless it is still
growing, even if it's very slowly.
If some people say "we want a separate Wikipedia for our mother
language" and another group says "we don't need a separate Wikipedia,
let's use the old one" but the first group says again "we still want
this separate Wikipedia, the current solution is not sufficient!", it
is inappropriate for the first group to be quashed by the second
simply because of a majority or minority.
We have some separate Wikipedias where we'd undoubtedly be able to get
by with a unified Wikipedia, but due to issues of nationalism, and
since it's never been done before, we haven't tried. But in the
opposite direction we have had a couple of similar issues. The
traditional vs simplified issue is thankfully now resolved (with the
exception of relatively minor outstanding issues), we have a separate
Wikipedia for Nynorsk, etc etc.
You talk about people adapting both ways. We aren't talking about
traditional vs simplified anymore.
For some time now, Mandarin has totally dominated other Sinitic
varieties and in some places there is the stereotype that a Mandarin
speaker expects everybody to speak Mandarin, and if they don't, they
must be daft (not that everybody fits this stereotype). Accommodations
for Cantonese, Minnan, Hakka, Wu, Minbei, Gan, etc. are rarely made,
and when they are it's usually in minor local issues, and nowadays it
seems it mostly happens in Hong Kong, Macao, and Taiwan.
If I write a section of an article in colloquial Cantonese, and place
it on zh:, what will you do? I think there is a good chance you will
either remove it as "nonsense" or change it to baihua saying that you
are "fixing it" - if this weren't the case, zh: would be a very
muddled Wikipedia compared to what it is today.
As Stirling Newberry noted, there is a fairly recent phenomenon of
material emerging in "CWY" (colloquial cantonese). Similar signs have
been seen from other Sinitic languages (Haishanghua was published in
colloquial Wu an eternity ago, but other than that Wu hasn't exactly
had a blossoming separate literature; Hakka is starting to emerge as a
separate and acceptable variety in Taiwan), but right now I think that
by far the most pronounced "linguistic rebellion" (ie, assertion of
linguistic independence) is for Cantonese.
Also, a Cantonese Wikipedia would presumably use hanzi rather than
romanization, and thus would probably attract a larger crowd than
zh-min-nan does (as Bao noted earlier, the fact that it's written in
romanization is a turn-off for a lot of people).
The Cantonese dialect does have unique colorful
phrases and a
different linguistic culture that manifests itself in Cantopop, film
and cartoons. Some would seem foreign to "Mandarin" speakers. It would
be great to have these Cantonese-isms captured in some way that could
be done in a combined ZH Wikipedia.
There is an emerging Cantonese literature, as Stirling Newberry noted.
Mark