The general problem is that everything's a moving target; new capabilities come to the web browsers.... but often a year or two behind native app interfaces, or only for the latest versions. Android 2.3's browser is still hanging around out there, it's the IE 6 of the mobile web. :)
Boot2Gecko/Firefox OS is very interesting, but we don't have a lot of resources assigned to it right now. (Our Firefox OS app is based on the old PhoneGap-based web/native hybrid app codebase, but runs as a "pure" web app with no special on-device privileges.)
Currently the Wikipedia Zero team has ownership on the Firefox OS Wikipedia app as FxOS is mostly being rolled out in developing countries so that ties in with carrier relationships and preinstall agreements that are in that group's territory. If you're interested in helping out with refactoring it, some folks may be interested as well!
(Another initiative of interest is Chrome mobile apps -- I don't have a link handy but I've heard that Google's working on a Chrome-based web app runtime for at least Android phones that sounds similar to how Firefox for Android handles Firefox web apps, making them available "almost native" but with a specific browser runtime instead of the old crappy default browser.)
It might though be more interesting to try to bring progressive enhancement to the MediaWiki+MobileFrontend web interface; but it's tricky to make things like offline really work reliably without a lot of retooling of the frontend into JavaScript.
-- brion