I'm not sure if the focus of this discussion is clear to everyone. As I
understand it, the primary concern is with preventing vandalism of
prominently placed images, such as those on the Main Page. This is
handled by protecting the images. I take it that this is the only
administrative function UninvitedCompany (and others who would like
Commons to adopt more liberal adminship policies) proposes to use there.
Nobody is going to be going on blocking or deleting sprees.
This would be a good candidate for a technical solution, specifically
using the MediaWiki feature of user access levels. If the only adminship
function you need on Commons is protection, for the purpose of
protecting another project from vandalism, then it should be routine to
grant (only) that function to anyone who's an admin on said project. It
might even be possible to make this automatically part of adminship once
single login is implemented, but at that point I feel like I'm wandering
into pipe dream territory.
--Michael Snow