My impression is that a weblog can' t remplace a CMS, but you can use it as a similar tool. i.e. In a CMS you would like to have your personal resume, and it is easy to have it. In a weblog you would need to post your resume and have a link to the post. It's not natural. Think now the "files", "events calendar", "newsletters", etc.
Alex King has an excellent site but uses WP for blogging and their tools to have the complete site, the blog is a part of it.
I have decided to use WP as a CMS to me (like your idea!). I have problems, but I wish to resolve it.