Here I record and perhaps refine the steps required to relocate a wiki. The wiki pages themselves should move easily. But the external configuration adjustments will involve many steps.
Test case. I would like to move xpdx.org from my old ruby server to my most modern bay.wiki.org site. I'm motivated by wanting to add the RSS plugin which uses server-side machinery not available in ruby.
I add xpdx.org to wiki.config.json. See Config Notes
{ "admin": { "twitter":"12381352", "persona":"ward@c2.com" }, "farm": true, "security_type": "passportjs", "twitter_consumerKey": "eG2...", "twitter_consumerSecret": "ZnRQ...", "wikiDomains": { "159.203.254.26": {}, "bay.wiki.org": {}, "ports.fed.wiki.org": {}, "xpdx.org": {} } }
restart wiki
I update nginx. /etc/nginx/sites-enabled/default
server { listen 80; server_name xpdx.org *.xpdx.com *.wiki.org ...
service nginx restart
I transfer the flat files with rsync or scp.
rsync -a fed.wiki.org:farm/xpdx.org . rsync -a xpdx.org root@bay.wiki.org:.wiki/
chown -R root:root .wiki/xpdx.org
I update the dns record at name.com. site 
I visit the new location, claim xpdx.org with that host's security, and add the RSS plugin.
Here I list my writings on the practices I find useful now. Read them, try them, and practice until they work for you. Add us to your blog reader.
Now I must repeat the transfer and claim process for for each of xpdx.org's subdomains.