Nice. I'm all for that, but like azrael said,
"The only bad part about this idea is finding time for Shawn to let a bunch of us in and work the site. The content of the site stays the same, but we just convert the entire site to php. If Shawn is working 45 hour weeks and has a life, we're going to have to drag him out of bed and drop him in front of a computer and let him do his part."
That's easier said than done actually.
Go with something like Mambo, where the admins can grant certain members access to contribute content to the site which has to ultimately be approved by the admin in order to be published.
My company's intranet is run entirely on Mambo and PHP, and it is a great system once you get it set up.
So is it secure too?