Gentlemen, let's say one is afraid one day the forces of evil will confiscate one's small wiki, so one wants to encourage all loyal users to keep a backup of the whole wiki (current revisions fine, no need for full history).
OK, we want this to be as simple as possible for our loyal users, just one click needed. (So forget Special:Export!)
And, we want this to be as simple as possible for our loyal administrator, me. I.e., use existing facilities, no cronjobs to run dumpBackup.php (or even mysqldump, which would be giving up too much information) and then offering a link to what they produce.
The format desired is for later making a new wiki via Special:Import, so indeed the Special:Export or dumpBackup.php --current outputs are the desired format.
I just can't figure out the right http://www.mediawiki.org/wiki/API URL recipe... api.php ? action=query & generator=allpages & format=xmlfm & ...? Could it be that the API lacks the "bulk export of XML formatted data" capability of Special:Export?
If one click is not enough, then at least one click per Namespace. I would just have the users backup Main: and Category:, for example.
Embedding the API URL would be no problem, I would just use [{{SERVER}}/api.php?... Backup this whole site to your disk]