planetsim.
Think of it this way:
A nice, pretty icon sits on the client desktop. Double clicked, it goes to the admin section of the site, asks for a password (as usual). It looks more like an application than a browser because 1) No resize- I can design with pix because I will know the client's resolution, 2) no address bar 3) no buttons across the top.
It puts a lot of emphasis on good navigation within the admin section.
I was even thinking of compiling the "browser" with the website logo (specific to each website).
It's just an idea right now.