The one problem I see that has not been adequately addressed is this:

Everyone actively participating in the project is already doing what
they have chosen to do. They are invested in the contributions they are
already making. Since I don't hear anyone enthusiastically dropping
their work to contribute to a central wiki, or diverting their efforts
toward contributions to one, I don't think you have been persuasive
enough in your cause. That's the political work I think that still needs
doing.

The current conversation is a beginning. But only a small beginning.

Since this discussion has gone on for a while, I would suggest you
review the previous discussion and summarize it. Include the positives
of the idea. Address each negative that has been mentioned on a point by
point basis. Then describe a plan for establishing the wiki. The plan
should include what effort/role you would play in establishing the wiki
and what is needed by others. It should also include what would be
required to maintain it.

In short, make an organized case for it. If it sounds well thought out
and is thorough enough, maybe then people will buy into it.

Remember that people's attention is scattered. They are busy,
distracted, and invested elsewhere. Following a long, drawn out
conversation like this is tough. If it gets too tough, people will stop
following along. Since you are the one trying to make a case, you have
to do the bulk of the work. Asking people to work extra to understand
what you are saying is asking a lot. (No, I'm not going to go back a
re-read everything. I'm just going to give you my suggestions as I see
them right now.)

I recognize that what I'm saying may sound annoying and/or condescending
but I don't mean it that way at all. I think you have a great idea but,
as I said above, I don't think it has been presented as well as it could
be nor as well as it needs to be in order to get the support it needs to
be successful.