Hi, GREAT idea for a plugin. I've been wrestling with this for a couple of days now.
I'd actually like something slightly different, as I wrote in another post. I host several WP installs on a single IP as virtual hosts. Something like this plugin could allow this sort of function so that admins can do their work through SSL:
http://www.foo.com/blogs = https://www.admin.com/foo/blogs
http://www.bar.com/blogs = https://www.admin.com/bar/blogs
... and so on.
But of course WordPress doesn't allow this. Could https-for-wordpress be easily modified to do this?
John