Is it possible to to do a HTTP redirect via URI and have anything after the / rediect as well?

I think I understand your request.

If you are just changing the host that the content is served from, but the URI is the same, this iRule should do what you need:

  when HTTP_REQUEST {
    set oldSite "old.sharepoint.net"
    set newSite "new.sharepoint.com"
    set testUri "/sites/migrationtesting/"

    if {([HTTP::host] equals $oldSite) and ([HTTP::uri] starts_with $testUri)} {
        HTTP::redirect "https://$newSite[HTTP::uri]"
    }

}