I'd say
that wikipedia should be used as a summary page, rather than an
exhaustive resource with app-specific documentation. So, I guess in that
respect I do agree with your ideas. However, I do not see it as an
exhaustive documentation resource for every app.
I think that is what the Wikipedia policies also have in mind. I
thought that the point, from the subject, was attracting more
developers (and non-Linux users, especially). For that purpose,
Wikipedia is probably a much better starting point than a more
Linux-centric site.
As for the specific documentation, my suggestion is to limit the
number of wikis. One is really better than three. It means less
maintenance work for the maintainers (and thanks to those who decide
to do it). It will be much easier for a community of this limited size
to clean up the vandalism of spammers or correct mistakes than
dividing our efforts among three locations. Maybe most importantly, if
I have a question, I don't have to go to three different places to
look for the information. Similarly, if I have documentation to
contribute, I don't have to go three places to add it.