Content Managment System Needed

I need a Content Management System that meets certain requirements for an RPG project. I can't find one that has everything I need or even one that has almost everything I need and I can wedge in some other components to cover the rest. So much to my chagrin it looks like I am going to have spend a whole lot of time writing a CMS when I really don't want to. Just for the hope that someone might be aware of something here are the requirements.

Absolutely Positively Must Have

• Linux / Apache / MySQL 4.1+ / PHP 4.3+ Based
• Search engine friendly URLs - URL rewriting if needed - inline links must have friendly URLs as well - no overtly dynamic URLs with querystrings and the like.
• Must have a category/tagging system similar to wordpress, must support sub-categories.
• Blog / News - A multi user blog is preferable to a news system and must work with categories/tags in a technorati friendly way.
• RSS - Must support all major feed types, RSS/Atom etc.
• User registration system - a simple user registration system that doesn't require much to get started.
• Articles - Managed article system which must also work with categories/tags.
• Downloads - Managed download system which must also work with categories.
• Must be able to run multiples sites (Site A, Site B, Site C) but only utilize a single user base.
• Must also be templated using XHTML and CSS - should not use tables for layout.
• Built in wiki and/or MediaWiki integration including users.
• A simple online store what again works with categories/tags
• Modular - must be able to add additional features/extensions in a modular fashion

Nice to have - not required

• Ajax functionality

I know it's a tall order but that's what I need (in brief.) If anyone knows of any CMS that comes even close to this please let me know. If it's open source I'd be willing to diverge a new system from the old.

Deluxe Basic Role Playing Status

Chaosium's Deluxe Basic Role Playing is still under development and seems to be progressing well. The chapter on powers is undergoing major revision at present and the writer, Jason Durall, has stated that the chapter should be released to testing very soon. The powers chapter is the only one that required major revision. The other chapters are undergoing minor revision and will be posted along with the powers chapter.

Overall the play testing has been going very well. Feedback during the play test has been on topic and to the point not to mention prolific. In fact there is so much useful feedback that it is taking some time for Jason to get all of the changes into that latest version. I unfortunately haven't really been able to get a group together for testing so I have had to limit myself primarily to more hypothetical testing.

I expect that once Jason releases the updated files for play testing they will undergo a relatively short test cycle (they should be pretty refined at that point) and then go to layout. I think everyone, especially Chaosium, is hoping to see the rules published by the time for Continuum (July 28th - 31st) and GenCon (August 10th - 13th.)

One other note:

Chaosium is interested in publishing BRP monographs and they would love it if they could have some monographs ready for the summer conventions mentioned above.

You can find their monograph submission guidelines here.