I'm not building a complex CMS just for my own site... (that would be a silly waste of time!).
It would only be a silly waste of time if you coded it in a clown costume and let out an exaggerated sigh whenever you got stumped. Then of course you would reach up and squeeze your big red nose bulb, filling the office with a resounding honk and wheeze. Then some guy would pop out of a nearby closet and start playing a funny song on the trombone. This would obviously cause you to start flailing around in a giggly clown dance.
I've been doing much reading about the semantic web over the last year or so, and likewise musing how a future CMS should work, while cobbling together layers over an existing work in progress CMS.
For ease of use for CMS users I don't think you will ever beat something which allows them to "edit in place" and then use an intelligent wysiwyg editor. (read/write web).
The case would be users browses website, sees and error clicks edit button and edits the page/paragraph.
It will have to automatically issue CoolURIs, without me having to manually set up Apache url rewrites.
It will automatically try and create or prompt for RDF descriptions, maybe using linked data, to describe and share what the content is actually about.
I think any CMS that can address those fairly simple technical requirements will have a chance getting itself into the running as a basic CMS core engine that can be extended to suit a particular niche, and would likely get my support.
Edit in place is a definite feature I am planning and I already have clean URIs in place. A few Apache rewrite rules are required to redirect everything except media files to the index.php, and then the index uses the URI to locate the content in a hierarchical structure. When you set up a new website, you create menus to create the hierarchical layout and point each menu item to a module (blog, contact, etc) or static page.
As for RDF.. This is the first I've heard of RDF, but it sounds interesting...
No offense, but I just don't like MODx. Maybe if I were forced to use it, I might change my mind once I got used to it. Though I don't doubt it may fulfill most of the wishes in this forum, I'm just asking what everyone wants in a CMS since I'm making my own anyway