Hi Ataryu,
I know exactly what your after, but i too am unsure of how to accomplish this. I use Frontpage 2003 to manage my web site, but it's only me that needs to edit it. Does the website in question have a data base, if so maybe there's a PHP script that could do the job, where the user can just log in and upload through their browser, a bit like an administrator of a forum, i can do nearly everything on my forum just by using my browser, might be worth a quick search!.
There must be something out there that could do the job. Most sites guest's books are just plain HTML but rely on SSI's to generate the info onto a page, so maybe there's some sort of work around with that too..........you could set a password for a plain page with the guest book entry form on it (so your editors could privately add context) then have the the main page people browse to set as where that context is displayed. Just an idea.....don't know how you would make a whole site from that though

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If i find something on my travels i will post back,
Chief.
EDIT>>> i just found something while searching for scripts
click here , This may not be what your looking for, but the rest of the site may hold something.