Hello,
Cant we remove the IT person's involvement too in inital setup? Also in your scenario, you have written like,
4. On each client site a windows service to poll for the latest version string and if a new version is found, download it, unpack it, apply the localised web.config, copy it to a new branch of the web site and then use IIS Manager to switch from old branch to new.
How can we programaticaly switch from old branch to new one in IIS Manager?