It might also be worth going a "wikibase" release (on its own schedule or else scheduled shortly after each MW release), that contains a particular MW version along with version of the extensions that have been tested to work with it. This is the usual way in which these sorts of dependency chains are dealt with outside of WMF. (Ie, when RedHat Fedora is released, it contains the latest GNOME at that time, which in turn contains a version of GTK+ and various utilities all tested to work well together).
For the admin, it should just be a matter of using "wikibase 1.23" or whatever; they shouldn't have to hunt down individual extensions and figure out compatible versions for themselves. --scott